Geometrical properties of embedded electrode structures for acoustic filters

Abstract

An apparatus for implementing an acoustic filter with an embedded electrode structure having certain geometric properties is disclosed. In example aspects, the geometric properties of the embedded electrode structure can be tailored to enhance the performance of the acoustic filter in terms of insertion loss, temperature stability, quality factor, and spurious mode suppression. Furthermore, the geometric properties can enable the acoustic filter to be tuned for a particular frequency range and / or bandwidth, to fit within a space-constrained device, and to improve manufacturing ease. Various performance improvements and design requirements can be met using the embedded electrode structure, as the geometric properties of the embedded electrode structure provide additional degrees of freedom in designing the acoustic filter. This design freedom enables the performance of the acoustic filter to be optimized in the presence of multiple complex interdependencies.

Description

Technical Field

[0001] This disclosure relates generally to wireless transceivers and other components employing filters, and more specifically to acoustic filters having an embedded electrode structure with specific geometric properties. Background Technology

[0002] Electronic devices use radio frequency (RF) signals to transmit information. These RF signals enable users to talk to friends, download information, share pictures, remotely control home appliances, and receive GPS information. To transmit or receive RF signals within a given frequency band, electronic devices can use filters to allow signals within the band to pass and suppress (e.g., reduce) interference or noise at frequencies outside the band. However, optimizing filters to provide filtering for RF applications can be challenging. In particular, the interdependencies between various design parameters can make it challenging to implement filters with specific frequency responses and bandwidths while meeting size constraints to fit within space-constrained devices. Summary of the Invention

[0003] An apparatus is disclosed that realizes an acoustic filter with an embedded electrode structure having specific geometric properties. In an example, the geometry of the embedded electrode structure can be customized to enhance the performance of the acoustic filter in terms of insertion loss, temperature stability, quality factor, and spurious mode suppression. Furthermore, this geometry allows the acoustic filter to be tuned for a specific frequency range and / or bandwidth for fitting within space-constrained devices and improving ease of manufacture. Various performance improvements and design requirements can be met using the embedded electrode structure because its geometry provides additional degrees of freedom in designing the acoustic filter. This design freedom enables the optimization of the acoustic filter's performance even in the presence of multiple complex interdependencies.

[0004] In an example, a device for filtering is disclosed. The device includes an acoustic filter having a piezoelectric layer and an electrode structure. The piezoelectric layer has two opposing surfaces forming a first plane and a second plane, respectively. The electrode structure is at least partially embedded within the piezoelectric layer. The electrode structure includes a plurality of fingers positioned across a first axis. The metallization ratio associated with the plurality of fingers is greater than about 0.2. Each of the plurality of fingers has a cross-section with a flat surface perpendicular to the first plane. The cross-section has a first segment adjacent to the first plane. The cross-section also has a second segment between the first plane and the second plane. A tangent positioned at a point along the edge of the cross-section forms an exterior angle relative to the first axis. The value of the exterior angle ranges from about 50° to 120°. The edge of the cross-section connects the first segment to the second segment.

[0005] In one example, a filtering apparatus is disclosed. The apparatus includes an acoustic filter configured to generate a filtered signal from a radio frequency (RF) signal. The acoustic filter includes a component for generating a formed sound wave. The component has two opposing surfaces forming a first plane and a second plane, respectively. The acoustic filter further includes a component for converting the RF signal into a sound wave and the formed sound wave into the filtered signal. The conversion component is at least partially embedded within the generation component. The conversion component includes a plurality of fingers positioned across a first axis. The metallization ratio associated with the plurality of fingers is greater than about 0.2. Each of the plurality of fingers has a cross-section with a flat surface perpendicular to the first plane. The cross-section has a first segment adjacent to the first plane. The cross-section also has a second segment between the first plane and the second plane. A tangent positioned at a point along the edge of the cross-section forms an exterior angle relative to the first axis. The value of the exterior angle ranges from about 50° to 120°. The edge of the cross-section connects the first segment to the second segment.

[0006] In one example, a method for manufacturing a filter is disclosed. The method includes: providing a piezoelectric layer having two opposing surfaces forming a first plane and a second plane, respectively. The method also includes: providing an electrode structure at least partially embedded within the piezoelectric layer. The electrode structure includes a plurality of fingers positioned across a first axis. The metallization ratio associated with the plurality of fingers is greater than about 0.2. Each of the plurality of fingers has a cross-section with a flat surface perpendicular to the first plane. The cross-section has a first segment adjacent to the first plane and a second segment between the first plane and the second plane. A tangent positioned at a point along the edge of the cross-section forms an exterior angle relative to the first axis. The value of the exterior angle ranges from about 50° to 120°. The edge of the cross-section connects the first segment to the second segment.

[0007] In an example, an acoustic filter is disclosed. The acoustic filter includes a piezoelectric layer having two opposing surfaces forming a first plane and a second plane, respectively. The acoustic filter also includes an electrode structure comprising a plurality of fingers positioned across a first axis. At least a portion of each of the plurality of fingers extends from the first plane toward the second plane. The metallization ratio associated with the plurality of fingers is greater than about 0.2. The cross-section of each of the plurality of fingers has a quadrilateral shape, the quadrilateral shape having segments facing the second surface and sidewalls forming outer angles with lines extending from a base. The value of the outer angle has a range from about 50° to 120°. Attached Figure Description

[0008] Figure 1An example operating environment for operating an acoustic filter with an embedded electrode structure is illustrated.

[0009] Figure 2 An example wireless transceiver is illustrated, which includes at least one acoustic filter with an embedded electrode structure.

[0010] Figure 3-1 An example component of an acoustic filter with an embedded electrode structure is shown.

[0011] Figure 3-2 An example Euler angle is shown to define the orientation of the piezoelectric layer of an acoustic filter with an embedded electrode structure.

[0012] Figure 4-1 An example implementation of a surface acoustic wave filter with an embedded electrode structure is illustrated.

[0013] Figure 4-2 An example implementation of a thin-film surface acoustic wave filter with an embedded electrode structure is illustrated.

[0014] Figure 4-3 An example implementation of a high-quality temperature-compensated surface acoustic wave filter with an embedded electrode structure is illustrated.

[0015] Figure 5-1 An example embedded electrode structure for an acoustic filter is shown.

[0016] Figure 5-2 An example cross-section of a finger with an embedded electrode structure is shown.

[0017] Figure 6 Examples of interdependencies between bandwidth, spurious mode suppression, and size for various geometries of embedded electrode structures are illustrated.

[0018] Figure 7 Example frequency responses are illustrated for specific implementations of acoustic filters with and without embedded electrode structures.

[0019] Figure 8 The effect of metallization ratio on the frequency response of an acoustic filter with an embedded electrode structure is illustrated.

[0020] Figure 9 An example is given of the angle of frequency response for an acoustic filter with an embedded electrode structure.

[0021] Figure 10 The effect of height on the frequency response of an acoustic filter with an embedded electrode structure is illustrated.

[0022] Figure 11The effect of metallization ratio on the frequency response of a high-quality temperature-compensated surface acoustic wave filter with an embedded electrode structure is illustrated.

[0023] Figure 12 This is a flowchart illustrating an example process for manufacturing an acoustic filter with an embedded electrode structure having specific geometric properties. Detailed Implementation

[0024] To transmit or receive radio frequency signals within a given frequency band, electronic devices may use filters to allow signals within the band to pass and suppress (e.g., attenuate) interference or noise with frequencies outside the band. Electroacoustic devices (e.g., “acoustic filters”) can be used in many applications to filter high-frequency signals, such as those with frequencies greater than 100 MHz. Acoustic filters are tuned to allow certain frequencies (e.g., frequencies within their passband) to pass and attenuate other frequencies (e.g., frequencies outside their passband). Using piezoelectric materials, acoustic filters operate by converting an electrical signal wave applied to an electrical conductor into an acoustic wave (e.g., an acoustic signal wave) formed across the piezoelectric material. The acoustic wave is then converted back to an electrically filtered signal. Acoustic filters may include electrode structures that transform or convert between electromagnetic waves and acoustic waves.

[0025] Sound waves are characterized by a speed much smaller than that of electromagnetic waves. Generally speaking, the speed of wave propagation is proportional to the wavelength of the wave. Therefore, after converting an electrical signal wave into a sound signal wave, the wavelength of the sound signal wave is significantly smaller than the wavelength of the electrical signal wave. The resulting smaller wavelength of the sound signal wave allows for the use of smaller filter devices to perform filtering. This permits the use of acoustic filters in space-constrained devices, including portable electronic devices such as cellular phones.

[0026] Design a system that can work with Wi-Fi at higher frequencies (such as 2.4 GHz, 5 GHz, frequencies greater than 5 GHz, frequencies below 6 GHz, frequencies between 6 GHz and 18 GHz, and / or frequencies greater than or equal to 10 GHz). ® Acoustic filters that provide filtering at frequencies used together can be challenging. Specifically, designing a filter that can be fitted into space-constrained devices, is easily fabricated, supports high-frequency and / or wide-bandwidth applications, supports carrier aggregation, and / or achieves target performance levels in terms of insertion loss, temperature stability, quality factor, and spurious mode suppression can be challenging. This challenge arises at least in part from the interdependence between size, bandwidth, and spurious modes. Therefore, many filters are designed with specific trade-offs that optimize performance in the first aspect while sacrificing performance in the second.

[0027] Some acoustic filters (such as thin-film surface acoustic wave filters) exhibit lower insertion loss and improved temperature stability, but mounting them in space-constrained devices can be challenging. Other acoustic filters (such as high-quality temperature-compensated filters) achieve specific temperature stability at the cost of reduced bandwidth. High-quality temperature-compensated filters may also lack sufficient spurious mode suppression, which can degrade the acoustic filter's performance for carrier aggregation.

[0028] To provide certain performance improvements, techniques are employed to implement acoustic filters with embedded electrode structures possessing specific geometric properties. In practice, the geometry of the embedded electrode structure can be tailored to enhance the performance of the acoustic filter in terms of insertion loss, temperature stability, quality factor, and spurious mode suppression. Furthermore, this geometry allows the acoustic filter to be tuned for specific frequency ranges and / or bandwidths, enabling it to be fitted into space-constrained devices and improving ease of manufacture. Various performance improvements and design requirements can be met using embedded electrode structures because their geometry provides additional degrees of freedom in designing acoustic filters. This design freedom allows for the optimization of acoustic filter performance even in the presence of multiple complex interdependencies.

[0029] Figure 1 An example environment 100 for operating an acoustic filter with an embedded electrode structure is illustrated. In environment 100, a computing device 102 communicates with a base station 104 via a wireless communication link 106 (wireless link 106). In this example, the computing device 102 is depicted as a smartphone. However, the computing device 102 can be implemented as any suitable computing or electronic device, such as a modem, cellular base station, broadband router, access point, cellular phone, gaming device, navigation device, media device, laptop computer, desktop computer, tablet computer, wearable computer, server, network-attached storage (NAS) device, smart appliance or other Internet of Things (IoT) device, medical device, vehicle-based communication system, radar, radio device, and so on. The use of acoustic filters is not limited to wireless communication, as acoustic filters can be applied to any technical field where such filtering is useful.

[0030] Base station 104 communicates with computing device 102 via wireless link 106, which can be implemented as any suitable type of wireless link. Although depicted as a cellular network tower, base station 104 can represent or be implemented as another device, such as a satellite, server equipment, terrestrial television broadcasting tower, access point, peer-to-peer device, mesh network node, etc. Therefore, computing device 102 can communicate with base station 104 or another device via a wireless connection.

[0031] Wireless link 106 may include a downlink transmitting data or control information from base station 104 to computing device 102, an uplink transmitting other data or control information from computing device 102 to base station 104, or both downlink and uplink. Wireless link 106 may be implemented using any suitable communication protocol or standard, such as 2G, 3G, 4G, 5G, or 6G cellular; IEEE 802.11 (e.g., Wi-Fi). ® ); IEEE 802.15 (e.g., Bluetooth) ® ); IEEE 802.16 (e.g., WiMAX) ® ); etc. In some implementations, the wireless link 106 may provide power wirelessly, and the base station 104 or computing device 102 may include a power source.

[0032] As shown in the figure, computing device 102 includes an application processor 108 and a computer-readable storage medium 110 (CRM 110). The application processor 108 may include any type of processor, such as a multi-core processor, that executes processor-executable code stored in the CRM 110. The CRM 110 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), etc. In the context of this disclosure, the CRM 110 is implemented to store instructions 112, data 114, and other information of computing device 102, and therefore does not include transiently propagated signals or carrier waves.

[0033] The computing device 102 may also include an input / output port 116 (I / O port 116) and a display 118. The I / O port 116 enables data exchange or interaction with other devices, networks, or users. The I / O port 116 may include a serial port (e.g., a Universal Serial Bus (USB) port), a parallel port, an audio port, an infrared (IR) port, a user interface port such as a touchscreen, etc. The display 118 displays graphics from the computing device 102, such as a user interface associated with an operating system, program, or application. Alternatively or additionally, the display 118 may be implemented as a display port or virtual interface through which the graphical content of the computing device 102 is displayed.

[0034] The wireless transceiver 120 of computing device 102 provides connectivity to a suitable network and other electronic devices connected thereto. The wireless transceiver 120 facilitates communication over any suitable type of wireless network, such as a wireless local area network (WLAN), peer-to-peer (P2P) network, mesh network, cellular network, ultra-wideband (UWB) network, wireless wide area network (WWAN), and / or wireless personal area network (WPAN). In the context of example environment 100, the wireless transceiver 120 enables computing device 102 to communicate with base station 104 and the network connected thereto. However, the wireless transceiver 120 also enables computing device 102 to communicate "directly" with other devices or networks.

[0035] Wireless transceiver 120 includes circuitry and logic for transmitting and receiving communication signals via antenna 122. Components of wireless transceiver 120 may include amplifiers, switches, mixers, analog-to-digital converters, filters, etc., for conditioning communication signals (e.g., for generating or processing signals). Wireless transceiver 120 may also include logic for performing in-phase / quadrature (I / Q) operations such as synthesis, encoding, modulation, decoding, demodulation, etc. In some cases, components of wireless transceiver 120 are implemented as separate transmitter and receiver entities. Additionally or alternatively, wireless transceiver 120 may be implemented using multiple or different parts to achieve corresponding transmit and receive operations (e.g., separate transmit and receive chains). Generally, wireless transceiver 120 processes data and / or signals associated with data transmitted through antenna 122 from computing device 102.

[0036] exist Figure 1 In the example shown, the wireless transceiver 120 includes at least one acoustic filter 124 (e.g., a type of surface acoustic wave (SAW) filter). In some specific embodiments, the wireless transceiver 120 includes a plurality of acoustic filters 124, which may be formed by acoustic resonators arranged in series, in parallel, in a trapezoidal structure, in a grid structure, or some combination thereof. The acoustic filter 124 includes at least one piezoelectric layer 126 and at least one electrode structure 128. The electrode structure 128 is at least partially embedded within the piezoelectric layer 126, as per [reference to...]. Figure 5-1 Further description.

[0037] The geometry 130 of the electrode structure 128 is optimized to improve the performance of the acoustic filter 124 relative to a similar acoustic filter 124 having an electrode structure disposed on the surface of the piezoelectric layer and not embedded within the piezoelectric layer. Regarding Figure 3-1Example geometry 130 is further described. Embedding electrode structure 128 within piezoelectric layer 126 provides additional degrees of freedom to optimize the design of acoustic filter 124. Using the described techniques, acoustic filter 124 can be designed to fit within space-constrained devices, is easy to manufacture, supports high-frequency and / or wide-bandwidth applications, supports carrier aggregation, and / or achieves target performance levels in terms of insertion loss, temperature stability, quality factor, and spurious mode suppression.

[0038] Using these improvements, the acoustic filter 124 can support frequency ranges above 2 GHz, including frequencies between approximately 2 GHz and 20 GHz. For example, the acoustic filter 124 can be designed to have resonant frequencies between approximately 4 GHz and 18 GHz, between approximately 7.5 GHz and 15 GHz, or equal to approximately 4 GHz, 5 GHz, 6 GHz, 10 GHz, 13 GHz, 15 GHz, 17 GHz, or 20 GHz. Generally, the term "approximately" can mean that any frequency is within + / - 10% of the specified value or less (e.g., within + / - 5%, + / - 3%, or + / - 2% of the specified value).

[0039] The acoustic filter 124 may be implemented as a surface acoustic wave filter 132 (SAW filter 132), a thin film (TF) surface acoustic wave (TFSAW) filter 134 (TFSAW filter 134), a high-quality temperature-compensated (HQ-TC) surface acoustic wave filter 136 (HQ-TC SAW filter 136), or another type of surface acoustic wave filter not shown. Figure 4-1 , Figure 4-2 ,and Figure 4-3 Examples of surface acoustic wave (SAW) filters 132, 134 (thin-film SAW), and 136 (high-quality temperature-compensated SAW) are shown respectively. Regarding... Figure 2 The acoustic filter 124 is further described.

[0040] Figure 2An example wireless transceiver 120 is illustrated. In the depicted configuration, the wireless transceiver 120 includes a transmitter 202 and a receiver 204, which are coupled to a first antenna 122-1 and a second antenna 122-2, respectively. In other specific embodiments, the transmitter 202 and receiver 204 may be connected to the same antenna via a duplexer (not shown). The transmitter 202 is shown as including at least one digital-to-analog converter 206 (DAC 206), at least one first mixer 208-1, at least one amplifier 210 (e.g., a power amplifier), and at least one first acoustic filter 124-1. The receiver 204 includes at least one second acoustic filter 124-2, at least one amplifier 212 (e.g., a low-noise amplifier), at least one second mixer 208-2, and at least one analog-to-digital converter 214 (ADC 214). The first mixer 208-1 and the second mixer 208-2 are coupled to a local oscillator 216. Although not explicitly shown, the digital-to-analog converter 206 of transmitter 202 and the analog-to-digital converter 214 of receiver 204 may be coupled to ( Figure 1 The application processor 108 or another processor (e.g., a modem) associated with the wireless transceiver 120.

[0041] In some implementations, the wireless transceiver 120 is implemented using multiple circuits (e.g., multiple integrated circuits), such as transceiver circuitry 236 and radio frequency front-end (RFFE) circuitry 238. Therefore, the components forming the transmitter 202 and receiver 204 are distributed across these circuits. Figure 2 As shown, transceiver circuitry 236 includes a digital-to-analog converter 206 for transmitter 202, a mixer 208-1 for transmitter 202, a mixer 208-2 for receiver 204, and an analog-to-digital converter 214 for receiver 204. In other embodiments, digital-to-analog converter 206 and analog-to-digital converter 214 may be implemented on a separate circuit including application processor 108 or modem. RF front-end circuitry 238 includes an amplifier 210 for transmitter 202, an acoustic filter 124-1 for transmitter 202, an acoustic filter 124-2 for receiver 204, and an amplifier 212 for receiver 204.

[0042] During transmission, transmitter 202 generates an RF transmission signal 218 transmitted using antenna 122-1. To generate the RF transmission signal 218, digital-to-analog converter 206 provides a pre-up-converted transmission signal 220 to first mixer 208-1. The pre-up-converted transmission signal 220 can be a baseband signal or an intermediate frequency (IF) signal. First mixer 208-1 uses a local oscillator (LO) signal 222 provided by local oscillator 216 to up-convert the pre-up-converted transmission signal 220. First mixer 208-1 generates an up-converted signal, referred to as pre-filter transmission signal 224. Pre-filter transmission signal 224 can be an RF signal and includes some noise or unwanted frequencies, such as harmonic frequencies. Amplifier 210 amplifies the pre-filter transmission signal 224 and passes the amplified pre-filter transmission signal 224 to first acoustic filter 124-1.

[0043] The first acoustic filter 124-1 filters the amplified pre-filtered transmit signal 224 to generate a filtered transmit signal 226. As part of the filtering process, the first acoustic filter 124-1 attenuates noise or unwanted frequencies within the pre-filtered transmit signal 224. The transmitter 202 provides the filtered transmit signal 226 to the antenna 122-1 for transmission. The transmitted filtered transmit signal 226 is represented by the radio frequency transmit signal 218.

[0044] During reception, antenna 122-2 receives radio frequency (RF) signal 228 and transmits it to receiver 204. Second acoustic filter 124-2 receives the received RF signal 228, which is represented by pre-filtered received signal 230. Second acoustic filter 124-2 filters any noise or unwanted frequencies within the pre-filtered received signal 230 to generate a filtered received signal 232.

[0045] Amplifier 212 of receiver 204 amplifies the filtered received signal 232 and passes the amplified filtered received signal 232 to second mixer 208-2. Second mixer 208-2 uses local oscillator signal 222 to down-convert the amplified filtered received signal 232 to generate a down-converted received signal 234. Analog-to-digital converter 214 converts the down-converted received signal 234 into a digital signal, which can be processed by application processor 108 or another processor (e.g., a modem) associated with wireless transceiver 120.

[0046] Figure 2An example configuration of the wireless transceiver 120 is illustrated. Other configurations of the wireless transceiver 120 may support multiple frequency bands and share antenna 122 across multiple transceivers. Those skilled in the art will understand that various other configurations may include the acoustic filter 124. For example, the acoustic filter 124 may be integrated within the duplexer or dual-channel unit of the wireless transceiver 120. Regarding... Figure 3-1 Example implementations of acoustic filters 124-1 or 124-2 are further described.

[0047] Figure 3-1 An example component of an acoustic filter 124 is illustrated. In the depicted configuration, the acoustic filter 124 includes a piezoelectric layer 126 and an electrode structure 128. Depending on the specific implementation, the acoustic filter 124 may optionally include a substrate stack 302, at least one compensation layer 304, at least one passivation layer 306, or some combination thereof.

[0048] In specific implementations, the piezoelectric layer 126 can be implemented using a variety of different materials exhibiting piezoelectric properties (e.g., the ability to convert mechanical energy into electrical energy or vice versa). Example types of materials include lithium niobate (LiNbO3) material 308, lithium tantalate (LiTaO3) material 310, quartz, aluminum nitride (AlN), scandium aluminum nitride (AlScN), or some combination thereof. Generally, the material forming the piezoelectric layer 126 has a crystalline structure. This crystalline structure is defined by the ordered arrangement of particles (e.g., atoms, ions, or molecules). The orientation of the crystal structure of the piezoelectric layer 126 can be defined by Euler angles 312 Å, lambda(λ), mu(µ), and theta(θ), see reference... Figure 3-2 These angles are further described. The crystal structure is operable to excite acoustic waves propagating along the surface of the piezoelectric layer 126, as described above. Figures 4-1 to 4-3 Further description.

[0049] In some aspects, the material and crystal structure of the piezoelectric layer 126 are selected such that one or more modes can be excited along the surface of the piezoelectric layer 126 in a desired direction. The material and / or crystal structure may also be selected to achieve a specific bandwidth. Consider an example in which the piezoelectric layer 126 is formed using lithium niobate material 308. In a first example embodiment, the lithium niobate material 308 is shaped such that the value of the Euler angle mu (µ) is between about -70° and -50°, and the values ​​of the Euler angles lambda (λ) and theta (θ) are approximately equal to 0° (or at least one symmetric equivalent thereof). In a second example embodiment, the lithium niobate material 308 is shaped such that the value of the Euler angle theta (θ) is between about -65° and -55°, and the values ​​of the Euler angles lambda (λ) and mu (µ) are approximately zero (or at least one symmetric equivalent thereof). Generally, the term "about" can mean that any angle is within ±10% of a specified value or less (e.g., within ±5%, ±3%, or ±2% of a specified value). The example Euler angles 312 mentioned above in the first and second exemplary embodiments can be used to implement a surface acoustic wave filter 123 capable of exciting higher-order modes. However, these angles are presented by way of example and not limitation. Other cuts can be made to achieve a piezoelectric layer 126 for the surface acoustic wave filter 123 that can be formed from lithium niobate or other materials. Furthermore, other Euler angles 312 (and other materials) can be selected to implement other types of acoustic filters, such as a thin-film surface acoustic wave filter 134 or a high-quality temperature-compensated surface acoustic wave filter 136.

[0050] Generally, Euler angle 312 can be selected to facilitate the excitation of one or more desired modes. In some cases, the excited modes can be higher-order modes, such as second-order, third-order, fourth-order, fifth-order, etc. In the example implementation, higher-order modes may be associated with frequencies between approximately 5 GHz and 20 GHz.

[0051] The material of piezoelectric layer 126 and the orientation of its propagation surface affect several performance parameters related to the crystal structure of the material. Example performance parameters include the electromechanical coupling coefficient (k...). 2 The electromechanical coupling factor (EMF) is determined by factors including the temperature coefficient of frequency (TCF), the mode or type of the generated sound wave, and other performance parameters. The EMF characterizes the efficiency of the acoustic filter 124 in converting between electrical and mechanical energy. Compared to another filter with a lower EMF, a filter with a higher EMF experiences less insertion loss and improved impedance matching over a wider frequency range. One way to define the EMF is further shown in Equation 1 below: Equation 1 Where f s It is the resonant frequency, and f pThis is the anti-resonant frequency. As an example, the electromechanical coupling coefficient of the acoustic filter 124 can be between approximately 5% and 35%.

[0052] The frequency temperature coefficient characterizes the amount by which the resonant frequency or skirt of a filter changes in response to temperature variations. A filter with a smaller absolute value of its frequency temperature coefficient exhibits a more stable frequency response over a given temperature range compared to another filter with a larger absolute value. The thickness of the piezoelectric layer 126 can be customized to provide mode suppression (e.g., suppression of stray plate modes), achieve a target electromechanical coupling factor, achieve a target frequency temperature coefficient, or some combination thereof.

[0053] Electrode structure 128 comprises a conductive material (such as a metal) and may include one or more layers. The one or more layers may include one or more conductive layers and may optionally include one or more adhesive layers, and may also optionally include one or more diffusion-blocking layers. As an example, the conductive layer may be composed of aluminum (Al), copper (Cu), silver (Ag), gold (Au), platinum (Pt), tungsten (W), silicon (Si), or some combination or doping form thereof. The adhesive layer may be composed of chromium (Cr), titanium (Ti), molybdenum (Mo), or some combination thereof. The diffusion-blocking layer may be composed of alumina (Al₂O₃), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), or some combination thereof. In some specific embodiments, the material of electrode structure 128 may be tailored to achieve a specific pitch that facilitates fabrication and / or adjusts the frequency response of acoustic filter 124 (e.g., increases the resonant frequency).

[0054] Electrode structure 128 may include one or more interdigital transducers 314. Interdigital transducers 314 convert electrical signals into acoustic waves and acoustic waves into filtered electrical signals. Interdigital transducers 314 include at least two comb structures 316-1 and 316-2. Each comb structure 316-1 and 316-2 includes a busbar 318 (e.g., a conductive segment or conductive rail) and a plurality of fingers 320 (e.g., electrode fingers). Regarding... Figures 4-1 to 4-3 The example interdigital transducer 314 is further described. Although not explicitly shown, the electrode structure 128 may also include two or more reflectors. In the example embodiment, the interdigital transducer 314 is arranged between two reflectors.

[0055] Electrode structure 128 is at least partially embedded within piezoelectric layer 126. The geometry 130 of electrode structure 128 provides additional degrees of freedom in designing acoustic filter 124 and achieving specific performance characteristics. Example geometry 130 includes metallization ratio 322, angle 324 (or exterior angle), and height 326.

[0056] The metallization ratio 322 represents the average width of adjacent fingers 320 divided by the pitch of the interdigital transducer 314. The pitch can represent the average distance between adjacent fingers 320 of the interdigital transducer 314. The metallization ratio 322 can be represented by the Greek letter eta (η). Generally, increasing the metallization ratio 322 can improve spurious mode suppression at the cost of increasing the size of the acoustic filter 124 and / or decreasing the bandwidth of the acoustic filter 124, as discussed regarding... Figure 6 and Figure 8 Further description.

[0057] Angle 324 represents an exterior angle formed at least in part by the tangent at a point along the cross section of the finger 320. Figure 5-1 and Figure 5-2 An example angle 324 is depicted. Generally, increasing the angle 324 increases the bandwidth of the acoustic filter 124 and improves spurious mode suppression at the cost of increasing the size of the acoustic filter 124, as shown in the section on... Figure 9 Further description.

[0058] Height 326 indicates the height of the finger 320 embedded within the piezoelectric layer 126. Figure 5-1 and Figure 5-2 The height 326 is further described in the text. Generally speaking, increasing the height 326 reduces the size of the acoustic filter 124 and increases the bandwidth of the acoustic filter 124 at the cost of reduced spurious mode suppression, as discussed in... Figure 10 Further description.

[0059] Some specific implementations of the acoustic filter 124 (e.g., Figure 4-2 The thin-film surface acoustic wave filter 134 may include a substrate stack 302. The substrate stack 302 may optionally include at least one compensation layer 328, optionally include at least one charge trapping layer 330, and include at least one substrate layer 332 (or support layer). It is possible to implement the substrate stack 302 using a single layer (e.g., substrate layer 332) or using multiple layers (e.g., multiple substrate layers 332 or some combination of substrate layer 332, compensation layer 328, and / or charge trapping layer 330). Generally, the substrate stack 302 includes one or more layers that can support passivation, temperature compensation, power handling, mode suppression, etc. In some specific embodiments, the substrate stack 302 may not include the compensation layer 328 and / or charge trapping layer 330 to reduce the cost of the acoustic filter 124.

[0060] The compensation layer 328 provides temperature compensation, enabling the acoustic filter 124 to achieve a target frequency temperature coefficient based on the thickness of the piezoelectric layer 126. In some embodiments, the thickness of the compensation layer 328 can be tailored to provide mode suppression (e.g., suppression of stray plate modes). In example embodiments, the compensation layer 328 may be implemented using at least one silicon dioxide (SiO2) layer, at least one doped silicon dioxide layer, at least one silicon nitride (SiN) layer, at least one silicon oxynitride (SiON) layer, or some combination thereof.

[0061] The charge trapping layer 330 can suppress nonlinear substrate effects. The charge trapping layer 330 may include at least one polycrystalline silicon (poly-Si) layer (e.g., a polycrystalline silicon layer or polymorphic silicon layer), at least one amorphous silicon layer, at least one silicon nitride (SiN) layer, at least one silicon oxynitride (SiON) layer, at least one aluminum nitride (AlN) layer, diamond-like carbon (DLC), diamond, or some combination thereof.

[0062] The substrate 332 is made of a non-conductive material that provides isolation. Example materials include silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, sapphire, quartz, glass, diamond, or some combination or doped version thereof. The substrate 332 may have a specific crystal orientation to support the suppression or attenuation of stray modes. In some embodiments, the substrate 332 consists of multiple layers. These multiple layers may be formed using the same material or different materials.

[0063] Some specific implementations of the acoustic filter 124 may include a compensation layer 304 and / or a passivation layer 306. The compensation layer 304 is disposed on the piezoelectric layer 126 and provides temperature compensation so that the acoustic filter 124 can achieve a target frequency temperature coefficient based on the thickness of the piezoelectric layer 126. In an example implementation, the compensation layer 304 may be formed using silicon dioxide (SiO2) or some doped version thereof. Doped versions of silicon dioxide may include fluorine-doped silicon dioxide (e.g., silicon oxyfluoride (SiO2)). x F y ) or carbon-doped silicon dioxide (e.g., SiO2) x C y In some applications, acoustic filter 124 may not include, for example, compensation layer 304, to reduce the cost of acoustic filter 124.

[0064] Passivation layer 306 may be disposed on compensation layer 304 or piezoelectric layer 126. In an example embodiment, passivation layer 306 is formed using silicon nitride (Si3N4). Passivation layer 306 protects the underlying layers from the influence of the external environment. The thickness of passivation layer 306 can also be used to adjust the frequency of acoustic filter 124.

[0065] In some respects, the acoustic filter 124 can be considered a resonator. Sometimes, the acoustic filter 124 can be connected to other resonators associated with a stack of layers different from the acoustic filter 124. In other respects, the acoustic filter 124 can be implemented as multiple interconnected resonators using the same layers (e.g., piezoelectric layer 126, electrode structure 128, substrate stack 302, compensation layer 304, and / or passivation layer 306). Further details... Figure 3-2 Various aspects of piezoelectric layer 126 are described.

[0066] Figure 3-2 An example Euler angle 312 is illustrated to define the orientation of the piezoelectric layer 126 relative to the crystal structure of the material forming the piezoelectric layer 126. In this example, the material forming the piezoelectric layer 126 includes lithium niobate and / or lithium tantalate. A first crystallographic (X') axis 334, a second crystallographic (Y') axis 336, and a third crystallographic (Z') axis 338 are fixed along the crystallographic axes of the crystal. A first rotation 340-1 is applied to rotate the first crystallographic X' axis 334 and the second crystallographic Y' axis 336 about the third crystallographic Z' axis 338. Specifically, the first rotation 340-1 rotates the first crystallographic X' axis 334 in the direction of the second crystallographic Y' axis 336. The angle associated with the first rotation 340-1 represents one Euler angle in the Euler angle 312, which is denoted by the Euler angle lambda(λ) 342. The resulting rotation axes are represented by a new set of axes: X'' axis 342, Y'' axis 344, and Z'' axis 346. Figure 3-2 As shown, the Z' axis 338 of the third crystal remains unchanged by the first rotation 340-1, so that the Z' axis 338 of the third crystal is equal to the Z'' axis 346.

[0067] In the second rotation 340-2, the Y'' axis 344 and Z'' axis 346 are rotated about the X'' axis 342 by another Euler angle 312, which is denoted by the Euler angle mu (µ) 348. In this case, the Y'' axis 344 is rotated in the direction of the Z'' axis 346. The resulting axes of rotation are represented by a new set of axes: X''' axis 350, Y''' axis 352, and Z''' axis 354. Figure 3-2 As shown, the X'' axis 342 remains unchanged by the second rotation 340-2, such that the X'' axis 342 is equal to the X''' axis 350.

[0068] In the third rotation 340-3, the X''' axis 350 and Y''' axis 352 are rotated about the Z''' axis 354 by an additional Euler angle 312, which is represented by the Euler angle theta (θ) 356. In this case, the X''' axis 350 is rotated along the direction of the Y''' axis 352. The resulting rotation axes are represented by the first filter (X) axis 358, the second filter (Y) axis 360, and the third filter (Z) axis 362, which correspond to... Figures 4-1 to 4-3 The first (X) axis 410, the second (Y) axis 412, and the third (Z) axis 414. For example... Figure 3-2 As shown, the Z''' axis 354 remains unchanged through the third rotation 340-3, making the Z''' axis 354 equal to the third filter Z-axis 362. Regarding... Figures 4-1 to 4-3 An example implementation of the acoustic filter 124 is further described.

[0069] Figure 4-1 A first example implementation of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. In this example, the acoustic filter 124 is implemented as a surface acoustic wave filter 132. Figure 4-1 The top shows a three-dimensional perspective view 400-1 of the surface acoustic wave filter 132, and... Figure 4-1 The bottom shows a two-dimensional cross-sectional view 400-2 of a portion of the surface acoustic wave filter 132.

[0070] The surface acoustic wave filter 132 includes a piezoelectric layer 126 and an electrode structure 128. In some example embodiments, the piezoelectric layer 126 includes a lithium niobate material 308. The lithium niobate material 308 is shaped such that the value of Euler angle mu (µ) 348 is between approximately -70° and -50°, and the values ​​of Euler angles lambda (λ) 340 and theta (θ) 356 are approximately 0° (or at least one symmetric equivalent thereof). The electrode structure 128 may include one or more interdigital transducers 314 (IDT 314). In the configuration depicted in the two-dimensional cross-sectional view 400-2, the electrode structure 128 is at least partially embedded within the piezoelectric layer 126.

[0071] In the three-dimensional perspective view 400-1, the interdigital transducer 314 is shown having two comb-like structures 316-1 and 316-2, wherein fingers 320 extend from two busbars 318 toward each other. The fingers 320 are interlocked between the two busbars 318 of the interdigital transducer 314 (e.g., arranged in an interdigital manner). In other words, the fingers 320 connected to the first busbar 318 extend toward the second busbar 318 but are not connected to it. Therefore, a barrier region 402 (e.g., a lateral gap region) exists between the end of the first finger 320 and the second busbar 318. Similarly, the fingers 320 connected to the second busbar 318 extend toward the first busbar 318 but are not connected to it. Therefore, a barrier region 402 exists between the end of these fingers 320 and the first busbar 318.

[0072] Along the direction of the generatrix 318, there is an overlap region 404 in which a portion of one finger 320 overlaps with a portion of an adjacent finger 320. This overlap region 404 may be referred to as an aperture, track, or active region, in which an electric field is generated between the fingers 320 to cause an acoustic wave 406 to form at least in this region of the piezoelectric layer 126.

[0073] The physical periodicity of the fingers 320 is referred to as the pitch 408 of the interdigital transducers 314. The pitch 408 can be indicated in various ways. For example, in some aspects, the pitch 408 may correspond to a magnitude of the distance between adjacent fingers 320 of the interdigital transducers 314 in the overlap region 404. For example, this distance may be defined as the distance between the center points of each finger in the fingers 320. When the fingers 320 have a uniform width, this distance can typically be measured between the right (or left) edge of one finger 320 and the right (or left) edge of the adjacent finger 320. In some aspects, the average distance between adjacent fingers 320 of the interdigital transducers 314 can be used for the pitch 408. The frequency of the piezoelectric layer 126 vibration is the principal resonant frequency of the electrode structure 128. This frequency is determined at least in part by the pitch 408 of the interdigital transducers 314 and other properties of the surface acoustic wave filter 132.

[0074] In the three-dimensional perspective view 400-1, the surface acoustic wave filter 132 is defined by a first (X) axis 410, a second (Y) axis 412, and a third (Z) axis 414. The first axis 410 and the second axis 412 are parallel to the flat surface of the piezoelectric layer 126, and the second axis 412 is perpendicular to the first axis 410. The third (Z) axis 414 is orthogonal (e.g., perpendicular) to the flat surface of the piezoelectric layer 126. The generatrix 318 of the interdigital transducer 314 is oriented parallel to the first axis 410. The fingers 320 of the interdigital transducer 314 are oriented parallel to the second axis 412. In other words, the longitudinal axis of the fingers 320 is substantially parallel to the second axis 412. The orientation of the piezoelectric layer 126 causes acoustic waves 406 to form primarily in the direction of the first axis 410. Therefore, acoustic waves 406 are formed in a direction substantially perpendicular to or orthogonal to the direction of the fingers 320 of the interdigital transducer 314. about Figure 4-2 Another type of acoustic filter 124 is further described.

[0075] Figure 4-2 A second example implementation of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. In this example, the acoustic filter 124 is implemented as a thin-film surface acoustic wave filter 134. Figure 4-2 The top shows a three-dimensional perspective view 400-3 of the thin-film surface acoustic wave filter 134, and... Figure 4-2 The bottom of the image shows a two-dimensional cross-sectional view 400-4 of a portion of the thin-film surface acoustic wave filter 134.

[0076] The thin-film surface acoustic wave filter 134 includes a piezoelectric layer 126, an electrode structure 128, and a substrate stack 302. In some example embodiments, the piezoelectric layer 126 includes lithium tantalate material 310. The lithium tantalate material 310 may be shaped such that Euler angle 312 can excite higher-order modes. In the configuration depicted in the two-dimensional cross-sectional views 400-4, the electrode structure 128 is at least partially embedded within the piezoelectric layer 126. The piezoelectric layer 126 is disposed on the “top” of the substrate stack 302. A compensation layer 328 is disposed between the piezoelectric layer 126 and a charge trapping layer 330. The charge trapping layer 330 is disposed between the compensation layer 328 and the substrate layer 332.

[0077] The three-dimensional perspective view 400-3 of the thin-film surface acoustic wave filter 134 is similar to... Figure 4-1A three-dimensional perspective view 400-1 of the surface acoustic wave filter 132. However, the thin-film surface acoustic wave filter 134 also includes a substrate stack 302. With the substrate stack 302 included, some specific implementations of the thin-film surface acoustic wave filter 134 can be designed to have lower insertion loss and enhanced temperature stability compared to the surface acoustic wave filter 132. However, the thin-film surface acoustic wave filter 134 can have a larger size compared to the surface acoustic wave filter 132.

[0078] Figure 4-3 A third example implementation of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. In this example, the acoustic filter 124 is implemented as a high-quality temperature-compensated surface acoustic wave filter 136. Figure 4-3 A three-dimensional perspective view 400-5 of a high-quality temperature-compensated surface acoustic wave filter 136 is shown at the top, and... Figure 4-3 The bottom shows a two-dimensional cross-sectional view 400-6 of a portion of a high-quality temperature-compensated surface acoustic wave filter 136.

[0079] A high-quality temperature-compensated surface acoustic wave filter 136 includes a piezoelectric layer 126, an electrode structure 128, a compensation layer 304, and a passivation layer 306. In some example embodiments, the piezoelectric layer 126 comprises lithium niobate material 308. In the configuration depicted in the two-dimensional cross-sectional views 400-6, the electrode structure 128 is at least partially embedded within the piezoelectric layer 126. The compensation layer 304 and the passivation layer 306 are disposed on top of the piezoelectric layer 126 and the electrode structure 128. The compensation layer 304 is disposed between the passivation layer 306 and the piezoelectric layer 126.

[0080] A three-dimensional perspective view of the high-quality temperature-compensated surface acoustic wave filter 136, 400-5, is similar. Figure 4-1 A three-dimensional perspective view 400-1 of the surface acoustic wave filter 132. However, the high-quality temperature-compensated surface acoustic wave filter 136 also includes a compensation layer 304 and a passivation layer 306.

[0081] Generally speaking, Figure 4-1 Electrode structure 128 of surface acoustic wave filter 132 Figure 4-2 Thin-film surface acoustic wave filter 134 and Figure 4-3 A high-quality temperature-compensated surface acoustic wave filter 136 can be similar. Likewise, Figure 4-1 Surface acoustic wave filter 132, Figure 4-2 Thin-film surface acoustic wave filter 134 and Figure 4-3 The piezoelectric layer 126 of the high-quality temperature-compensated surface acoustic wave filter 136 can have similar materials and / or crystal structures. However, Figure 4-2The thickness of the piezoelectric layer 126 in the thin-film surface acoustic wave filter 134 can be significantly smaller than that of the thin-film surface acoustic wave filter 134. Figure 4-1 The thickness of the piezoelectric layer 126 of the surface acoustic wave filter 132 and / or the high-quality temperature-compensated surface acoustic wave filter 136.

[0082] During the operation, regarding Figures 4-1 to 4-3 Each of the acoustic filters described in the acoustic filters 124 accepts radio frequency signals, such as... Figure 2 The pre-filter transmit signal 224 or pre-filter receive signal 230 is shown. Electrode structure 128 uses the inverse piezoelectric effect to excite acoustic waves 406 within piezoelectric layer 126. For example, interdigital transducers 314 in electrode structure 128 generate an alternating electric field based on the received radio frequency signal. Piezoelectric layer 126 enables acoustic waves 406 to be formed in response to this alternating electric field generated by interdigital transducers 314. In other words, piezoelectric layer 126 at least partially enables acoustic waves 406 to be formed in response to electrical stimulation by one or more interdigital transducers 314.

[0083] Acoustic wave 406 is formed within piezoelectric layer 126 and interacts with interdigital transducer 314 or another interdigital transducer within electrode structure 128. Figures 4-1 to 4-3 (Not shown in the image) Interaction. The formed acoustic wave 406 can be a standing wave. Using the piezoelectric effect, the electrode structure 128 generates a filtered radio frequency signal based on the formed acoustic wave 406. Specifically, due to the mechanical stress generated by the acoustic wave 406, the piezoelectric layer 126 generates an alternating electric field. This alternating electric field induces an alternating current in the interdigital transducer 314. This alternating current forms a filtered radio frequency signal provided at the output of the acoustic filter 124. The filtered radio frequency signal may include... Figure 2 The filtered transmitted signal 226 or the filtered received signal 232.

[0084] It should be understood that, although in Figures 4-1 to 4-3 A certain number of fingers are illustrated, but the actual number of fingers, as well as the length and width of the fingers and busbars, may vary in actual implementations. These parameters depend on the specific application and desired filter characteristics. Furthermore, the acoustic filter 124 may include multiple interconnect electrode structures 128, each including multiple interdigital transducers 314 to achieve a desired passband (e.g., multiple interconnected resonators or interdigital transducers 314 connected in series or parallel to form a desired filter transfer function).

[0085] Although not explicitly shown, electrode structure 128 may also include two or more reflectors. In an example embodiment, interdigital transducers 314 are arranged between two reflectors (not shown). Each reflector within electrode structure 128 may have two busbars and grating structures with conductive fingers respectively connected to the two busbars. In some embodiments, the pitch of the reflectors may be similar to or the same as the pitch 408 of the interdigital transducers 314. Regarding Figure 5-1 The geometric properties 130 of the electrode structure 128 are further described.

[0086] Figure 5-1 A portion of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. Figure 5-1 The image shows a two-dimensional cross-sectional view of the acoustic filter 124 along axes 410 and 414. The piezoelectric layer 126 of the acoustic filter 124 has a first surface 502-1 and a second surface 502-2 opposite to the first surface 502-1. The first surface 502-1 may be referred to as the “top” surface of the piezoelectric layer 126, and the second surface 502-2 may be referred to as the “bottom” surface of the piezoelectric layer 126. In the case of a thin-film surface acoustic wave filter 134, the first surface 502-1 faces away from the substrate stack 302, and the second surface 502-2 faces the substrate stack 302. In the case of a high-quality temperature-compensated surface acoustic wave filter 136, the first surface 502-1 faces the compensation layer 304 and / or the passivation layer 306, and the second surface 502-2 faces away from the compensation layer 304 and / or the passivation layer 306. The first surface 502-1 forms a first plane 504-1, and the second surface 502-2 forms a second plane 504-2. The first and second planes 504-1 and 504-2 may be substantially parallel to each other. The first and second planes 504-1 and 504-2 extend along the first axis 410 and the second axis 412.

[0087] Electrode structure 128 is at least partially embedded within piezoelectric layer 126. In other words, at least a portion of electrode structure 128 is surrounded by or adjacent to piezoelectric layer 126. Electrode structure 128 has a first surface 506-1, which may be adjacent to or "above" the first plane 504-1 (as shown by the dashed line). Electrode structure 128 also has a second surface 506-2, which is opposite to and / or faces the second plane 504-2. Generally, the distance between the second surface 506-2 and the second plane 504-2 is less than the distance between the first surface 506-1 and the second plane 504-2. Electrode structure 128 is embedded such that the second surface 506-1 is positioned along a third axis 414 between the first plane 504-1 and the second plane 504-2.

[0088] exist Figure 5-1In the diagram, electrode structure 128 is shown comprising at least three fingers 320-1, 320-2, and 320-3 positioned across (e.g., arranged along) a first axis 410. The cross-section 508 of the fingers 320-1, 320-2, and 320-3 along the first axis 410 and the third axis 414 is shown to have a specific shape 510. Figure 5-1 In the cross-section 508, the shape 510 is quadrilateral (e.g., rectangular or trapezoidal). Other shapes 510 are also possible, such as triangles, semi-ellipses (e.g., half an ellipse), semicircles, etc. In the case of a quadrilateral, the electrode structure 128 is embedded within the piezoelectric layer 126 such that at least a portion of the three sides of the rectangular shape abuts or contacts the piezoelectric layer 126. In other words, portions of the three sides lie along the third axis 414 between the first and second planes 504-1 and 504-2.

[0089] Other specific implementations in which the dielectric material is disposed between the electrode structure 128 and the piezoelectric layer 126 are also possible. In this case, the electrode structure 128 may not be in physical contact with the piezoelectric layer 126, but may still be embedded within the piezoelectric layer 126 such that an axis parallel to the first axis 410 passes through the piezoelectric layer 126 and the fingers 320 of the electrode structure 128.

[0090] In the case of a quadrilateral, each finger 320 has a first segment 512 adjacent to a first plane 504-1 and a second segment 512-2 adjacent to a second plane 504-2. The first segment 512-1 represents a first surface 506-1 of the electrode structure 128, and the second segment 512-2 represents a second surface 506-2 of the electrode structure 128. The finger 320 also has two sidewalls 514 facing opposite directions. The sidewalls 514 connect segments 512-1 and 512-2 together.

[0091] A line extends from segment 512-2 along the first axis 410 to form an angle 324 with the sidewall 514. This angle 324 may also be referred to as the exterior angle of shape 510. In some embodiments, the length of the first segment 512-1 along the first axis 410 is greater than the length of the second segment 512-2 along the first axis 410. In this case, the angle 324 may be less than 90°. In other embodiments, the length of the first segment 512-1 along the first axis 410 is less than the length of the second segment 512-2 along the first axis 410. In this case, the angle 324 may be greater than 90° and less than 180°.

[0092] The height 326 of the electrode structure 128 is defined as the distance between the first segment 512-1 and the second segment 512-2. If the shape 510 is rectangular, as shown... Figure 5-1The height 326 depicted indicates the length of the sidewall 514. Regarding... Figure 5-2 Another example shape 510 of the cross section 508 of the finger 320 is further described.

[0093] Figure 5-2 An example cross-section 508 of the finger 320 of the electrode structure 128 is illustrated. In the depicted configuration, the cross-section 508 of the finger 320 is trapezoidal in shape. The trapezoid includes a first base 516-1, a second base 516-2, a first waist 518-1, and a second waist 518-2. The first and second bases 516-1 and 516-2 respectively represent Figure 5-1 The first and second segments 512-1 and 512-2. Waists 518-1 and 518-2 represent... Figure 5-1 The sidewall 514. In this case, the height 326 of the electrode structure 128 represents the distance between the first and second bottom edges 516-1 and 516-2 (e.g., the height 326 represents the vertical height of the trapezoid).

[0094] Angle 324 represents the exterior angle of the trapezoid. More specifically, angle 324 is formed between one of the legs 518-1 or 518-2 and a line extending from the second base 516-2 along the first axis 410. Generally, for any shape 510 of the cross-section 508, angle 324 is formed between the tangent 520 located at a point along the edge of the cross-section 508 and the first axis 410. This point is along the edge of the cross-section 508 and between the first and second planes 504-1 and 504-2.

[0095] By customizing two or more geometric properties 130 of the electrode structure 128, the acoustic filter 124 can achieve a target performance level. Example geometric properties 130 include the metallization ratio 322, angle 324, and / or height 326 of the electrode structure 128. Other aspects or characteristics of the acoustic filter 124 can also be customized, including the pitch 408, the material of the electrode structure 128, the material and cut of the piezoelectric layer 126, the thickness of one or more layers of the acoustic filter 124, etc. About Figure 6 The relationship between the metallization ratio 322, angle 324 and characteristics of the acoustic filter 124 is further described.

[0096] Figure 6 Examples of interdependencies between bandwidth, spurious mode suppression, and size for various geometries 130 of the embedded electrode structure 128 are illustrated. Figure 6 Three curves, 602, 604, and 606, are depicted. The metallization ratio 322 (e.g., eta) is depicted along the horizontal axis. Angle 324 is depicted along the vertical axis of these curves.

[0097] First graph 602 depicts the relationship between the metallization ratio 322, the angle 324, and the pole-zero distance (PZD). Different shading in graph 602 represents different pole-zero distances. Lighter shading indicates a larger pole-zero distance, while darker shading indicates a smaller pole-zero distance. The pole-zero distance determines the bandwidth of the acoustic filter 124. For broadband applications, it is desirable to design the acoustic filter 124 with a larger pole-zero distance. As seen in graph 602, a larger pole-zero distance can be achieved with a smaller metallization ratio 322 and a larger angle 324.

[0098] The second graph, 604, depicts the relationship between the metallization ratio 322, the angle 324, and stray mode suppression. Different shading in graph 604 represents different degrees of stray mode reduction. Lighter shading indicates less stray mode suppression, while darker shading indicates more stray mode suppression. As shown in graph 604, better stray mode suppression can be achieved using the metallization ratio 322 and angle 324 in the middle of graph 604.

[0099] The third graph, 606, depicts the relationship between the metallization ratio 322, the angle 324, and the static capacitance of the acoustic filter 124. Different shading in graph 606 represents different static capacitances. Lighter shading indicates larger static capacitance, while darker shading indicates smaller static capacitance. Static capacitance affects the overall footprint of the acoustic filter 124. An acoustic filter 124 with larger static capacitance can be implemented with a smaller footprint compared to other acoustic filters 124 with smaller static capacitance. Therefore, it may be desirable to design an acoustic filter 124 with a specific static capacitance so that the acoustic filter 124 can be fitted into space-constrained devices. As shown in graph 604, a larger static capacitance can be achieved with a larger metallization ratio 322 and a smaller angle 324.

[0100] Considering graphs 602, 604, and 606, bandwidth, spurious mode suppression, and static capacitance cannot be optimized individually due to their interdependence with the metallization ratio 322 and angle 324. However, these characteristics of the acoustic filter 124 can be optimized together by at least customizing the metallization ratio 322 and angle 324 of the embedded electrode structure 128. At 608 in graphs 602, 604, and 606, values ​​of the metallization ratio 322 and angle 324 are identified that optimize the bandwidth, spurious mode suppression, and size of the acoustic filter 124 for a specific application and / or for a specific set of requirements.

[0101] In an exemplary embodiment, electrode structure 128 may have a metallization ratio 322, the value of which is in the range of approximately greater than or equal to 0.2. Electrode structure 128 may also have an angle 324, the value of which is in the range of approximately 50° to 120°. For example, angle 324 may be approximately equal to 50°, 60°, 70°, 80°, 90°, 100°, 110°, or 120°. In some embodiments, angle 324 may also have a range of approximately 60° to 90° or from 90° to 120°. Optionally, electrode structure 128 may also have a height 326, the value of which is in the range of approximately 5% to 20% of the wavelength of acoustic wave 406. In an exemplary embodiment, the value of height 326 may have a range of approximately 100 nanometers (nm) to 500 nm. Generally speaking, the term "about" can mean that any value in the range is within + / - 10% of the specified value or less (e.g., within + / - 5%, + / - 3%, or + / - 2% of the specified value). For various types of filters, the range of values ​​can be further narrowed, as described below.

[0102] To optimize the performance of the surface acoustic wave filter 132, the metallization ratio 322 also has a value ranging from, for example, about 0.3 to 0.6. Furthermore, the angle 324 also has a value ranging from about 60° to 90°.

[0103] To optimize the performance of the thin-film surface acoustic wave filter 134, the metallization ratio 322 also has a value ranging from approximately 0.3 to 0.6. Furthermore, the angle 324 also has a value ranging from approximately 60° to 90°.

[0104] To optimize the performance of the high-quality temperature-compensated surface acoustic wave filter 136, the metallization ratio 322 has a value greater than or equal to 0.2. Furthermore, the angle 324 has a value ranging from approximately 60° to 90°.

[0105] The geometry 130 can also be customized to optimize additional characteristics of the acoustic filter 124, including insertion loss (e.g., electromechanical coupling coefficient) and temperature stability (e.g., frequency temperature coefficient). In some cases, the geometry 130 is customized to compensate for other design choices. By customizing the geometry 130 of the embedded electrode structure 128, and particularly the metallization ratio 322 and angle 324, the acoustic filter 124 can achieve better performance than other filters that do not utilize the embedded electrode structure. About Figure 7 An example frequency response of the acoustic filter 124 is further described.

[0106] Figure 7Example frequency responses of an acoustic filter 124 with an embedded electrode structure 128 and another acoustic filter with a non-embedded electrode structure are illustrated. Graph 700 depicts the frequency response 702 of the other acoustic filter using a dashed line. This other acoustic filter has a non-embedded electrode structure compared to the acoustic filter 124 described herein. Instead, the electrode structure is disposed on the surface of the piezoelectric layer.

[0107] Graph 700 also depicts the frequency response 704 of the acoustic filter 124 with embedded electrode structure 128 using a solid line. The geometry 130 of the embedded electrode structure 128 has a specific range of values ​​to enhance the performance of the acoustic filter 124 relative to another acoustic filter. Generally, the acoustic filter 124 can be a surface acoustic wave filter 132, a thin-film surface acoustic wave filter 134, or a high-quality temperature-compensated filter 136.

[0108] When comparing the frequency response 704 of acoustic filter 124 with the frequency response 702 of another acoustic filter, the admittance of acoustic filter 124 is higher than that of the other acoustic filter. The higher admittance indicates a higher static capacitance, which allows acoustic filter 124 to be implemented with a smaller footprint than the other acoustic filter.

[0109] In low-order mode 706 (or low-order excitation mode), frequency response 704 has a larger pole-zero distance compared to frequency response 702. Therefore, the frequency response 704 of acoustic filter 124 has a wider bandwidth relative to the frequency response 704 of another acoustic filter 124. Low-order mode 706 may correspond to, for example, a first-order mode or a second-order mode.

[0110] In higher-order mode 708 (or higher-order excitation mode), frequency response 704 has a larger peak admittance compared to frequency response 702. This means that frequency response 704 has less insertion loss in higher-order mode 708 compared to frequency response 702. Higher-order mode 708 may correspond to, for example, a third-order mode or a fifth-order mode. Generally speaking, higher-order mode 708 indicates a mode with a higher order than lower-order mode 706.

[0111] In an example embodiment of surface acoustic wave filter 132 or thin-film surface acoustic wave filter 134, low-order mode 706 represents a first-order mode centered at a frequency of approximately 2.5 GHz. Furthermore, high-order mode 708 represents a third-order mode centered at a frequency of approximately 8 GHz. In an example embodiment of high-quality temperature-compensated surface acoustic wave filter 136, low-order mode 706 represents a first-order mode centered at a frequency of approximately 1.8 GHz. Furthermore, high-order mode 708 is centered at a frequency of approximately 2.25 GHz.

[0112] The higher-order mode 708 enables the acoustic filter 124 to pass frequencies associated with multiple frequency bands. Therefore, the acoustic filter 124 can support a larger number of frequency bands compared to other acoustic filters. This means that the computing device 102 can be implemented with fewer acoustic filters 124, saving space within the computing device 102.

[0113] In summary, the technique for using the geometry 130 of the custom embedded electrode structure 128 enables the acoustic filter 124 to be fitted into space-constrained devices, supporting wide bandwidth and / or high frequency applications, and / or supporting carrier aggregation. Regarding Figures 8 to 10 The effects of adjusting various geometric properties 130 of the embedded electrode structure 128 are further described.

[0114] Figure 8 The effect of the metallization ratio 322 on the frequency response of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. Graph 800 depicts three frequency responses 802, 804, and 806 corresponding to the acoustic filter 124 with the embedded electrode structure 128, which has an increased metallization ratio 322. Frequency responses 802, 804, and 806 have a low-order mode 706 and a high-order mode 708.

[0115] Frequency responses 802, 804, and 806 are associated with metallization ratios 322-1, 322-2, and 322-3, respectively. The second metallization ratio 322-2 is greater than the first metallization ratio 322-1. Furthermore, the third metallization ratio 322-3 is greater than the second metallization ratio 322-2. Figure 8 In this context, the metallization ratios 322-1, 322-2, and 322-3 are equal to 0.4, 0.5, and 0.6, respectively. Other example values ​​are also possible.

[0116] By comparing frequency responses 802, 804, and 806, it can be seen that increasing the metallization ratio 322 increases the pole-zero distance and thus increases the bandwidth of the acoustic filter 124. It can also be seen that spurious modes 808 are introduced in frequency response 806. Therefore, increasing the metallization ratio 322 too much may degrade spurious mode suppression. Additionally, increasing the metallization ratio 322 increases the static capacitance of the acoustic filter 124. Therefore, the acoustic filter 124 with a frequency response 806 can be implemented with a smaller footprint compared to the acoustic filter 124 with frequency responses 802 and 804. Regarding insertion loss, increasing the metallization ratio 322 reduces the insertion loss under higher-order modes 708. For example, the acoustic filter 124 with a frequency response 806 experiences less insertion loss compared to the acoustic filter 124 with frequency responses 802 and 804. Angle 324 can also be customized to optimize the characteristics of the acoustic filter 124, as per [reference needed]. Figure 9 Further description.

[0117] Figure 9 The effect of angle 324 on the frequency response of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. Graph 900 depicts three frequency responses 902, 904, and 906 corresponding to the acoustic filter 124 with the embedded electrode structure 128 having an increased angle 324.

[0118] Frequency responses 902, 904, and 906 are associated with angles 324⁻¹, 324⁻², and 324⁻³, respectively. The second angle 324⁻² is greater than the first angle 324⁻¹. The third angle 324⁻³ is greater than the second angle 324⁻². Figure 9 In this case, angles 324-1, 324-2, and 324-3 are equal to 70°, 80°, and 90°, respectively. Other values ​​are also possible.

[0119] By comparing frequency responses 902, 904, and 906, it can be seen that increasing angle 324 alters the pole-zero distance and thus the bandwidth of acoustic filter 124. In higher-order mode 708, the bandwidth of frequency response 904 is greater than that of frequency responses 902 and 906. It can also be seen that spurious mode suppression depends on angle 324. For example, frequency response 902 exhibits poorer spurious mode suppression compared to frequency responses 904 and 906. Furthermore, increasing angle 324 reduces the static capacitance of acoustic filter 124. Therefore, acoustic filter 124 with frequency response 906 can have a larger footprint compared to acoustic filters 124 with frequency responses 902 and 904. Regarding insertion loss, increasing angle 324 reduces insertion loss in higher-order mode 708. For example, acoustic filter 124 with frequency response 906 experiences less insertion loss compared to acoustic filters 124 with frequency responses 902 and 904. Height 326 can also be customized to optimize the characteristics of acoustic filter 124, as per [reference needed]. Figure 10 Further description.

[0120] Figure 10 The effect of height 326 on the frequency response of an acoustic filter 124 with an embedded electrode structure 128 is illustrated. Graph 1000 depicts three frequency responses 1002, 1004, and 1006 corresponding to the acoustic filter 124 with the embedded electrode structure 128 having an increased height 326.

[0121] Frequency responses 1002, 1004, and 1006 are associated with altitudes 326-1, 326-2, and 326-3, respectively. The second altitude, 326-2, is greater than the first altitude, 326-1. The third altitude, 326-3, is greater than the second altitude, 326-2. Figure 10 In the figure, the heights 326-1, 326-2, and 326-3 are equal to 200nm, 300nm, and 400nm, respectively.

[0122] By comparing frequency responses 1002, 1004, and 1006, it can be seen that increasing the height 326 increases the pole-zero distance and thus increases the bandwidth of the acoustic filter 124. In higher-order mode 708, the bandwidth of frequency response 1006 is wider than that of frequency responses 1002 and 1004. It can also be seen that spurious mode suppression depends on the height 326. For example, frequency response 1004 has poorer spurious mode suppression compared to frequency responses 1002 and 1006. Furthermore, increasing the height 326 increases the static capacitance of the acoustic filter 124. Therefore, the acoustic filter 124 with a frequency response 1006 can have a smaller footprint compared to acoustic filters 124 with frequency responses 1002 and 1004. Regarding insertion loss, increasing the height 326 reduces the insertion loss in higher-order mode 708. For example, acoustic filter 124 with frequency response 1006 experiences less insertion loss compared to acoustic filter 124 with frequency responses 1002 and 1004.

[0123] about Figures 7 to 10 The example values ​​mentioned can be used to implement surface acoustic wave filter 132 or thin-film surface acoustic wave filter 134. Generally, surface acoustic wave filter 132 and thin-film surface acoustic wave filter 134 can be designed to support high-frequency applications (e.g., frequencies greater than 2.5 GHz).

[0124] Figures 7 to 10 The example values ​​can be further customized to achieve a high-quality temperature-compensated surface acoustic wave filter 136. By varying the metallization ratio 322, angle 324, and / or height 326, the high-quality temperature-compensated surface acoustic wave filter 136 can also exhibit similar effects in its frequency response. Generally, the high-quality temperature-compensated surface acoustic wave filter 136 is designed to support lower frequency applications (e.g., frequencies below 2.5 GHz). Therefore, the high-quality temperature-compensated surface acoustic wave filter 136 can excite low-order modes 706 and can optionally be designed to excite higher-order modes 708. Reference Figure 11 The frequency response of the example high-quality temperature-compensated surface acoustic wave filter 136 is further described.

[0125] Figure 11The effect of the metallization ratio 322 on the frequency response of a high-quality temperature-compensated surface acoustic wave filter 136 with an embedded electrode structure 128 is illustrated. Graph 1100 depicts two frequency responses 1102 and 1104 corresponding to an acoustic filter 124 with an embedded electrode structure 128 having an increased metallization ratio 322. Frequency responses 1102 and 1104 exhibit a low-order mode 706. Figure 11 In the middle, low-order mode 706 indicates a first-order mode centered at approximately 1.8 GHz. (This is related to the above regarding...) Figures 8 to 10 Compared to the described acoustic filter 124, Figure 11 The high-quality temperature-compensated surface acoustic wave filter 136 described in the paper essentially suppresses the higher-order mode 708.

[0126] Frequency responses 1102 and 1104 are associated with metallization ratios 322-1 and 322-2, respectively. The second metallization ratio 322-2 is greater than the first metallization ratio 322-1. Figure 11 In this study, the metallization ratios 322-1 and 322-2 are 0.4 and 0.7, respectively. Other values ​​are also possible.

[0127] By comparing frequency responses 1102 and 1104, it can be seen that increasing the metallization ratio 322 reduces the pole-zero distance and thus reduces the bandwidth of the acoustic filter 124. In low-order mode 706, the bandwidth of frequency response 1104 is narrower than that of frequency response 1102. It can also be seen that spurious mode suppression depends on the metallization ratio 322. For example, frequency response 1104 has better spurious mode suppression compared to frequency response 1102. In addition, increasing the metallization ratio 322 increases the static capacitance of the acoustic filter 124. Therefore, the acoustic filter 124 with frequency response 1104 can have a smaller footprint compared to the acoustic filter 124 with frequency response 1102. In terms of insertion loss, increasing the metallization ratio 322 increases the insertion loss in low-order mode 706. For example, the acoustic filter 124 with frequency response 1104 experiences more insertion loss compared to the acoustic filter 124 with frequency response 1102.

[0128] For the high-quality temperature-compensated surface acoustic wave filter 136, compared to another high-quality temperature-compensated surface acoustic wave filter with a non-embedded electrode structure, the embedded electrode structure 128 improves the pole-zero distance. This allows for an increase in the thickness of the compensation layer 304, which improves the frequency temperature coefficient.

[0129] Some high-quality temperature-compensated surface acoustic wave (SAW) filters may be sensitive to stray modes 1108 (e.g., plate modes). However, the geometry 130 of the embedded electrode structure 128 can be customized to suppress stray modes. For example, as Figure 11 As shown, the metallization ratio 322 can be increased to enhance spurious mode suppression. While the thickness of the compensation layer 304 can be reduced to improve spurious mode suppression, this reduces the pole-to-zero distance and thus the bandwidth of the high-quality temperature-compensated surface acoustic wave filter. The embedded electrode structure 128 can increase the pole-to-zero distance by a sufficient amount to compensate for this reduction. More specifically, the embedded electrode structure 128 provides an additional margin for the pole-to-zero distance, allowing the high-quality temperature-compensated surface acoustic wave filter 136 to be designed to fit within a given size constraint, achieve specific temperature stability, and provide sufficient spurious mode suppression.

[0130] Figure 12 This is a flowchart illustrating an example process 1200 for manufacturing an acoustic filter 124 with an embedded electrode structure 128. Process 1200 is described in the form of a set of boxes 1202 to 1204 specifying operable operations. However, the operations are not necessarily limited to... Figure 12 The order shown or described herein is not applicable, as these operations can be implemented in an alternative order or in a manner that is wholly or partially overlapping. Furthermore, more, fewer, and / or different operations can be implemented to perform process 1200 or alternative processes. Operations represented by the boxes exemplified by process 1200 can be performed to manufacture (e.g., Figure 1 , Figure 3-1 , Figure 4-1 , Figure 4-2 and Figure 4-3 (The) acoustic filter 124. More specifically, the operation of process 1200 may be performed at least in part to provide (e.g., Figures 6 to 11 An embedded electrode structure 128 with specific geometric properties 130 is used to optimize the performance of the acoustic filter 124.

[0131] At position 1202, a piezoelectric layer is provided having two opposing surfaces forming a first plane and a second plane, respectively. For example, the manufacturing process provides a piezoelectric layer 126. The piezoelectric layer 126 has two opposing surfaces 502-1 and 502-2 forming the first and second planes 504-1 and 504-2, respectively, as shown below. Figure 5-1 As shown.

[0132] At 1204, an electrode structure is provided that is at least partially embedded within the piezoelectric layer. This electrode structure includes a plurality of fingers positioned across a first axis. For example, the manufacturing process provides an electrode structure 128 that is at least partially embedded within the piezoelectric layer 126, such as... Figures 4-1 to 5-2As shown. Electrode structure 128 includes a plurality of fingers 320, which are positioned across a first axis 410, as... Figures 4-1 to 5-1 As shown.

[0133] The metallization ratio associated with the multiple fingers is greater than about 0.2. For example, the metallization ratio 322 associated with the multiple fingers 320 is greater than about 0.2. To implement the example surface acoustic wave filter 132 or the example thin-film surface acoustic wave filter 134, the metallization ratio also has a range of about 0.3 to 0.6. The metallization ratio 322 may, for example, be about 0.4, 0.5, or 0.6. To implement the example high-quality temperature-compensated surface acoustic wave filter 136, the metallization ratio 322 also has a range greater than about 0.2. For example, the metallization ratio 322 may be about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc.

[0134] Each of the plurality of fingers has a cross-section with a flat surface perpendicular to a first plane, the cross-section having a first segment adjacent to the first plane and a second segment between the first and second planes. A tangent located at a point along the edge of the cross-section forms an exterior angle relative to a first axis. The value of the exterior angle ranges from approximately 50° to 120°. The edge of the cross-section connects the first segment to the second segment.

[0135] For example, each of the plurality of fingers 320 has a cross-section 508 with a flat surface perpendicular to the first plane. The flat surface of the cross-section 508 may also be parallel to the first axis 410. The cross-section 508 has a first segment 512-1 adjacent to the first plane 504-1 and a second segment 512-2 between the first plane 504-1 and the second plane 504-2, as shown below. Figure 5-1 As shown. Tangent 520 is located at a point along the edge of cross-section 508 (e.g., along sidewall 514) and forms an exterior angle 324 relative to the first axis 410, as... Figure 5-1 and Figure 5-2 As shown. The edge of cross-section 508 connects the first segment 512-1 to the second segment 512-2, as... Figure 5-1 As shown.

[0136] The value of the exterior angle 324 has a range of approximately from 50° to 120°. To implement the example surface acoustic wave filter 132, the example thin-film surface acoustic wave filter 134, or the example high-quality temperature-compensated surface acoustic wave filter 136, the value of angle 324 also has a range of approximately from 60° to 90°. Angle 324 can, for example, be approximately equal to 70°, 80°, or 90°.

[0137] The following paragraphs describe some aspects of example implementations and / or example configurations related to the apparatus and / or process presented above.

[0138] Example aspect 1: An apparatus comprising: An acoustic filter, the acoustic filter comprising: A piezoelectric layer having two opposing surfaces that respectively form a first plane and a second plane; An electrode structure, at least partially embedded within the piezoelectric layer, the electrode structure comprising a plurality of fingers positioned across a first axis. The metallization ratio associated with the plurality of fingers is greater than about 0.2; Each of the plurality of fingers has a flat surface in its cross-section perpendicular to the first plane, the cross-section having: The first segment, which is adjacent to the first plane; and The second segment lies between the first plane and the second plane; and A tangent located at a point along the edge of the cross section forms an exterior angle relative to the first axis, the value of which has a range of approximately 50° to 120°, the edge of the cross section connecting the first segment to the second segment.

[0139] Example aspect 2: The apparatus according to example aspect 1, wherein the electrode structure is at least partially embedded within the piezoelectric layer such that at least a portion of the electrode structure extends from the first plane toward the second plane.

[0140] Example aspect 3: The apparatus according to example aspect 1 or 2, wherein the value of the outer angle also has a range of about 60° to 90°.

[0141] Example aspect 4: The apparatus according to any one of the foregoing example aspects, wherein the cross-section is trapezoidal in shape.

[0142] Example aspect 5: The apparatus according to example aspect 4, wherein: The trapezoid includes: The first bottom edge is adjacent to the first plane; The second base edge faces the second plane; and The waist connects the first bottom edge to the second bottom edge; The points along the edge of the cross-section include points along the waist; and The outer angle is formed between the waist and a line extending along the first axis beyond the second bottom edge.

[0143] Example aspect 6: The apparatus according to any one of the foregoing example aspects, wherein the metallization ratio represents the average width of adjacent fingers among the plurality of fingers divided by the average distance between adjacent fingers among the plurality of fingers.

[0144] Example aspect 7: The apparatus according to any one of the foregoing example aspects, wherein: The longitudinal axes of the plurality of fingers are substantially parallel to the second axis perpendicular to the first axis; The third axis is orthogonal to the first axis and the second axis; The orientations of the first axis, the second axis, and the third axis are relative to the crystal structure of the piezoelectric layer, as defined by Euler angles lambda(λ), mu(µ), and theta(θ); and The value of Euler angle mu (μ) has a range of approximately -70° to -55° or at least one symmetric equivalent.

[0145] Example aspect 8: The apparatus according to example aspect 7, wherein the values ​​of the Euler angles lambda (λ) and theta (θ) are approximately equal to 0°.

[0146] Example aspect 9: The apparatus according to example aspect 7 or 8, wherein the piezoelectric layer comprises lithium niobate (LiNbO3) material.

[0147] Example aspect 10: The apparatus according to any one of examples 7 to 9, wherein the acoustic filter is configured to excite two different orders of modes.

[0148] Example aspect 11: The apparatus according to example aspect 10, wherein one of the two modes includes a third-order mode associated with a frequency between about 5 GHz and 20 GHz.

[0149] Example aspect 12: The apparatus according to any one of example aspects 7 to 11, wherein: The acoustic filter is configured to excite sound waves having a wavelength; and The height of each of the plurality of fingers has a range of approximately 5% to 20% of the wavelength.

[0150] Example aspect 13: The apparatus according to any one of the foregoing example aspects, wherein: The acoustic filter includes a surface acoustic wave filter; The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.6.

[0151] Example aspect 14: The apparatus according to any one of example aspects 1 to 12, wherein: The acoustic filter includes a thin-film surface acoustic wave filter; The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.6.

[0152] Example aspect 15: An apparatus according to any one of example aspects 1 to 12, wherein: The acoustic filter includes a high-quality temperature-compensated surface acoustic wave filter. The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range greater than about 0.2.

[0153] Example aspect 16: The apparatus according to any one of the foregoing example aspects, wherein: The acoustic filter includes multiple cascaded resonators; and The resonator in the plurality of cascaded resonators includes the piezoelectric layer and the electrode structure.

[0154] Example aspect 17: The apparatus according to any one of the foregoing example aspects further includes: A wireless transceiver coupled to at least one antenna, the wireless transceiver including the acoustic filter and configured to use the acoustic filter to filter wireless signals transmitted via the at least one antenna.

[0155] Example aspect 18: An apparatus comprising: An acoustic filter, configured to generate a filtered signal from a radio frequency signal, the acoustic filter comprising: A component for generating the formed sound waves, the component having two opposing surfaces forming a first plane and a second plane respectively; and A component for converting the radio frequency signal into a sound wave and the generated sound wave into the filtered signal, the component for conversion being at least partially embedded within the component for generation, the component for conversion including a plurality of fingers positioned across a first axis. The metallization ratio associated with the plurality of fingers is greater than about 0.2; Each of the plurality of fingers has a flat surface in its cross-section perpendicular to the first plane, the cross-section having: The first segment, which is adjacent to the first plane; and The second segment lies between the first plane and the second plane; and A tangent located at a point along the edge of the cross section forms an exterior angle relative to the first axis, the value of which has a range of approximately 50° to 120°, the edge of the cross section connecting the first segment to the second segment.

[0156] Example aspect 19: The apparatus according to example aspect 18, wherein the cross-section is trapezoidal in shape.

[0157] Example aspect 20: The apparatus according to example aspect 18 or 19, wherein: The value of the outer angle also has a range of approximately 60° to 90°; and The acoustic filter includes a surface acoustic wave filter, a thin-film surface acoustic wave filter, or a high-quality temperature-compensated surface acoustic wave filter.

[0158] Example aspect 21: The apparatus according to any one of example aspects 18 to 20, wherein: The value of the metallization ratio also has a range of approximately from 0.3 to 0.6, and the acoustic filter includes a surface acoustic wave filter or a thin-film surface acoustic wave filter; or The value of the metallization ratio also has a range greater than about 0.2, and the acoustic filter includes a high-quality temperature-compensated surface acoustic wave filter.

[0159] Example aspect 22: A method for manufacturing an acoustic filter, the method comprising: A piezoelectric layer is provided, the piezoelectric layer having two opposing surfaces forming a first plane and a second plane, respectively; and An electrode structure is provided, the electrode structure being at least partially embedded within the piezoelectric layer, the electrode structure comprising a plurality of fingers positioned across a first axis, wherein: The metallization ratio associated with the plurality of fingers is greater than about 0.2; Each of the plurality of fingers has a flat surface in its cross-section perpendicular to the first plane, the cross-section having: The first segment, which is adjacent to the first plane; and The second segment lies between the first plane and the second plane; and A tangent located at a point along the edge of the cross section forms an exterior angle relative to the first axis, the value of which has a range of approximately 50° to 120°, the edge of the cross section connecting the first segment to the second segment.

[0160] Example aspect 23: According to the method described in example aspect 22, wherein: The longitudinal axes of the plurality of fingers are substantially parallel to the second axis perpendicular to the first axis; The third axis is orthogonal to the first axis and the second axis; The orientations of the first axis, the second axis, and the third axis are relative to the crystal structure of the piezoelectric layer, as defined by Euler angles lambda(λ), mu(µ), and theta(θ); and Providing the piezoelectric layer includes providing the piezoelectric layer such that the value of the Euler angle mu (μ) has a range of about -70° to -55° or at least one symmetrical equivalent.

[0161] Example aspect 24: According to the method of example aspect 23, providing the piezoelectric layer includes: giving the acoustic filter a frequency response capable of exciting two different orders of modes.

[0162] Example aspect 25: An acoustic filter, the acoustic filter comprising: A piezoelectric layer having two opposing surfaces forming a first plane and a second plane, respectively; and An electrode structure comprising a plurality of fingers positioned across a first axis, wherein at least a portion of each of the plurality of fingers extends from the first plane toward the second plane. The metallization ratio associated with the plurality of fingers is greater than about 0.2; and Each of the plurality of fingers has a quadrilateral shape in cross-section, the quadrilateral shape having a segment facing the second plane and sidewalls forming an exterior angle with a line extending from the segment, the value of the exterior angle having a range of approximately 50° to 120°.

[0163] Example aspect 26: An acoustic filter according to example aspect 25, wherein: The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.6.

[0164] Example aspect 27: According to the acoustic filter of example aspect 25, the acoustic filter further includes: A substrate stack, the substrate stack being adjacent to the second plane; The value of the outer angle also has a range of approximately 60° to 120°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.6.

[0165] Example aspect 28: According to the acoustic filter described in Example aspect 25, the acoustic filter further includes: A compensation layer, wherein the compensation layer is configured to be adjacent to the first plane; The value of the outer angle also has a range of approximately 50° to 80°; and The value of the metallization ratio also has a range greater than about 0.2.

[0166] Example aspect 29: An acoustic filter according to any one of Example aspects 25 to 28, wherein: The longitudinal axes of the plurality of fingers are substantially parallel to the second axis perpendicular to the first axis; The third axis is orthogonal to the first axis and the second axis; The orientations of the first axis, the second axis, and the third axis are relative to the crystal structure of the piezoelectric layer as defined by Euler angles lambda(λ), mu(µ), and theta(θ); The value of Euler angle mu (μ) has a range of approximately -70° to -55° or at least one symmetric equivalent. The values ​​of the Euler angles lambda(λ) and theta(θ) are approximately equal to 0°; and The piezoelectric layer comprises lithium niobate material.

[0167] Example aspect 30: An acoustic filter according to example aspect 29, wherein: The acoustic filter is configured to excite two different orders of modes based on the values ​​of the Euler angles lambda(λ), mu(μ), and theta(θ); and One of the two modes is associated with an order greater than or equal to the third order.

[0168] Unless the context otherwise specifies, the use of the word “or” in this document may be interpreted as “inclusive or” or as the use of a term that allows the inclusion or application of one or more items linked by the word “or” (e.g., the phrase “A or B” may be interpreted as allowing only “A”, only “B”, or both “A” and “B”). As used herein, the phrase “at least one of” in a list of items refers to any combination of those items, including a single member. As an example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c). Additionally, the items represented in the figures and the terms discussed herein may indicate one or more items or terms, and therefore the singular or plural forms of these items and terms may be referred to interchangeably in this written description. Finally, although the subject matter has been described in language specific to structural features or methodological operations, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including not necessarily limited to the arrangement of the features or the order in which the operations are performed.

Claims

1. An apparatus, the apparatus comprising: An acoustic filter, the acoustic filter comprising: A piezoelectric layer having two opposing surfaces that respectively form a first plane and a second plane; An electrode structure, at least partially embedded within the piezoelectric layer, the electrode structure comprising a plurality of fingers positioned across a first axis. The metallization ratio associated with the plurality of fingers is greater than about 0.2; Each of the plurality of fingers has a flat surface in its cross-section perpendicular to the first plane, the cross-section having: The first segment, which is adjacent to the first plane; and The second segment lies between the first plane and the second plane; and A tangent located at a point along the edge of the cross section forms an exterior angle relative to the first axis, the value of which has a range of approximately 50° to 120°, the edge of the cross section connecting the first segment to the second segment.

2. The apparatus of claim 1, wherein the electrode structure is at least partially embedded within the piezoelectric layer such that at least a portion of the electrode structure extends from the first plane toward the second plane.

3. The apparatus of claim 1, wherein the value of the outer angle further has a range of approximately 60° to 90°.

4. The device according to claim 1, wherein the cross-section is trapezoidal in shape.

5. The apparatus according to claim 4, wherein: The trapezoid includes: The first bottom edge is adjacent to the first plane; The second base edge faces the second plane; and The waist connects the first bottom edge to the second bottom edge; The points along the edge of the cross-section include points along the waist; and The outer angle is formed between the waist and a line extending along the first axis beyond the second bottom edge.

6. The apparatus of claim 1, wherein the metallization ratio represents the average width of adjacent fingers among the plurality of fingers divided by the average distance between adjacent fingers among the plurality of fingers.

7. The apparatus according to claim 1, wherein: The longitudinal axes of the plurality of fingers are substantially parallel to the second axis perpendicular to the first axis; The third axis is orthogonal to the first axis and the second axis; The orientations of the first axis, the second axis, and the third axis are relative to the crystal structure of the piezoelectric layer, as defined by Euler angles lambda(λ), mu(µ), and theta(θ); and The value of Euler angle mu (μ) has a range of approximately -70° to -55° or at least one symmetric equivalent.

8. The apparatus of claim 7, wherein the Euler angles lambda(λ) and theta(θ) are approximately equal to 0°.

9. The apparatus of claim 7, wherein the acoustic filter is configured to excite two different orders of modes based on the Euler angles lambda(λ), mu(μ), and theta(θ).

10. The apparatus according to claim 7, wherein: The acoustic filter is configured to excite sound waves having a wavelength; and The height of each of the plurality of fingers has a range of approximately 5% to 20% of the wavelength.

11. The apparatus according to claim 1, wherein: The acoustic filter includes a surface acoustic wave filter; The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.

6.

12. The apparatus according to claim 1, wherein: The acoustic filter includes a thin-film surface acoustic wave filter; The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.

6.

13. The apparatus according to claim 1, wherein: The acoustic filter includes a high-quality temperature-compensated surface acoustic wave filter. The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range greater than about 0.

2.

14. A method for manufacturing an acoustic filter, the method comprising: A piezoelectric layer is provided, the piezoelectric layer having two opposing surfaces that respectively form a first plane and a second plane; as well as An electrode structure is provided, the electrode structure being at least partially embedded within the piezoelectric layer, the electrode structure comprising a plurality of fingers positioned across a first axis, wherein: The metallization ratio associated with the plurality of fingers is greater than about 0.2; Each of the plurality of fingers has a flat surface in its cross-section perpendicular to the first plane, the cross-section having: The first segment is adjacent to the first plane; as well as The second segment lies between the first plane and the second plane; and A tangent located at a point along the edge of the cross section forms an exterior angle relative to the first axis, the value of which has a range of approximately 50° to 120°, the edge of the cross section connecting the first segment to the second segment.

15. The method of claim 14, wherein: The longitudinal axes of the plurality of fingers are substantially parallel to the second axis perpendicular to the first axis; The third axis is orthogonal to the first axis and the second axis; The orientations of the first axis, the second axis, and the third axis are relative to the crystal structure of the piezoelectric layer as defined by Euler angles lambda(λ), mu(µ), and theta(θ); and Providing the piezoelectric layer includes providing the piezoelectric layer such that the value of the Euler angle mu (μ) has a range of about -70° to -55° or at least one symmetrical equivalent.

16. An acoustic filter, the acoustic filter comprising: A piezoelectric layer having two opposing surfaces that respectively form a first plane and a second plane; as well as An electrode structure comprising a plurality of fingers positioned across a first axis, wherein at least a portion of each of the plurality of fingers extends from the first plane toward the second plane. The metallization ratio associated with the plurality of fingers is greater than about 0.3; and Each of the plurality of fingers has a quadrilateral shape in cross-section, the quadrilateral shape having a segment facing the second plane and sidewalls forming an exterior angle with a line extending from the segment, the value of the exterior angle having a range of approximately 50° to 120°.

17. The acoustic filter according to claim 16, wherein: The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.

6.

18. The acoustic filter according to claim 16, further comprising: A substrate stack, the substrate stack being adjacent to the second plane; The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range of approximately from 0.3 to 0.

6.

19. The acoustic filter according to claim 16, further comprising: A compensation layer, wherein the compensation layer is configured to be adjacent to the first plane; The value of the outer angle also has a range of approximately 60° to 90°; and The value of the metallization ratio also has a range greater than about 0.

2.

20. The acoustic filter according to claim 16, wherein: The longitudinal axes of the plurality of fingers are substantially parallel to the second axis perpendicular to the first axis; The third axis is orthogonal to the first axis and the second axis; The orientations of the first axis, the second axis, and the third axis are relative to the crystal structure of the piezoelectric layer as defined by Euler angles lambda(λ), mu(µ), and theta(θ); The value of Euler angle mu (μ) has a range of approximately -70° to -55° or at least one symmetric equivalent. The values ​​of the Euler angles lambda(λ) and theta(θ) are approximately equal to 0°; and The piezoelectric layer comprises lithium niobate material.

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