Thin-film surface acoustic wave resonators with aluminum nitride layers

Abstract

An apparatus for a surface acoustic wave (SAW) device having an aluminum nitride substrate layer is disclosed. In one aspect, a SAW includes: a substrate layer comprising an aluminum nitride (AlN) substrate layer, an electrode structure including interdigitated transducers, and a piezoelectric layer disposed between the electrode structure and the substrate layer. In some aspects, the piezoelectric layer is lithium niobate or lithium tantalate.

Description

Technical Field

[0001] This disclosure relates generally to filters, and more specifically to surface acoustic wave (SAW) filters having an aluminum nitride (AlN) layer. Background Technology

[0002] Electronic devices include traditional computing devices such as desktop computers, laptops, tablets, smartphones, wearable devices such as smartwatches, and internet servers. These diverse electronic devices provide human users with information, entertainment, social interaction, security, safety, productivity, transportation, manufacturing, and other services. Many of the functions of these diverse electronic devices rely on wireless communication. Wireless communication systems and devices are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, and broadcasting. These systems can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems (e.g., Long Term Evolution (LTE) systems or New Radio (NR) systems).

[0003] The wireless communication transceivers used in these electronic devices typically include multiple radio frequency (RF) filters for filtering signals at specific frequencies or frequency ranges. Electroacoustic devices (e.g., "acoustic filters") are used in many applications to filter high-frequency (e.g., typically greater than 100 MHz) signals. Using piezoelectric materials as the vibrating medium, acoustic resonators operate by converting electrical signal waves propagating along an electrical conductor into sound waves propagating through the piezoelectric material. Sound waves propagate at speeds much smaller than the propagation speed of electromagnetic waves. Generally, the magnitude of the wave propagation speed is proportional to the wavelength of the wave. Therefore, after converting an electrical signal into an acoustic signal, the wavelength of the acoustic signal wave is significantly smaller than the wavelength of the electrical signal wave. The resulting smaller wavelength of the acoustic signal allows for the use of smaller filter devices to perform filtering. This permits the use of acoustic resonators in electronic devices with size constraints, such as those listed above (e.g., specifically portable electronic devices such as cellular phones). Summary of the Invention

[0004] A device for implementing a surface acoustic wave (SAW) filter using an aluminum nitride (AlN) substrate is disclosed.

[0005] In one aspect, an apparatus is provided. The apparatus is a surface acoustic wave (SAW) filter device, comprising: a substrate layer comprising an aluminum nitride (AlN) substrate layer; an electrode structure comprising an interdigital transducer having an input terminal, an output terminal, and a center track; and a piezoelectric layer disposed between the electrode structure and the substrate layer, wherein the crystal structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ), wherein the substrate layer and the piezoelectric layer are configured for the excitation of a selected electroacoustic mode, the excitation of which is constrained by the AlN substrate layer to limit the excitation of stray modes in the stacked structure of the SAW filter device.

[0006] Some of these aspects are configured such that the piezoelectric layer contains lithium tantalate, and that the Euler angles used for the piezoelectric layer are selected in the range of LT0 to LT60.

[0007] On the other hand, there is a resonator device. This resonator device includes a SAW resonator, which includes a glass support layer and a fast AlN layer disposed on the glass support layer. Various aspects may additionally include a slow layer disposed on the AlN layer. Various aspects may also include an electrode structure including an interdigital transducer; and a piezoelectric layer disposed between the electrode structure and the fast layer.

[0008] Some of these aspects are configured such that the substrate layer and the piezoelectric layer are configured for the excitation of surface waves. Some of these aspects are configured such that the slow layer is a SiO2 layer configured to confine the excitation of stray surface waves.

[0009] Another method is described. This method includes: forming a substrate layer comprising an aluminum nitride (AlN) substrate layer; forming a piezoelectric layer on a top surface of the substrate layer, wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ); and forming an electrode layer on the top surface of the piezoelectric layer, wherein the substrate layer and the piezoelectric layer are configured for surface wave excitation, and wherein the AlN substrate layer is configured as a fast layer to confine stray wave excitation.

[0010] On the other hand, there is a device. The device is a surface acoustic wave (SAW) resonator, which includes a substrate layer including an aluminum nitride (AlN) substrate layer; an electrode structure including an interdigital transducer; and a piezoelectric layer disposed between the electrode structure and the substrate layer.

[0011] Some of these aspects are configured such that the substrate layer and the piezoelectric layer are configured for surface wave excitation, and the AlN substrate layer is configured as a fast layer to confine wave energy to the top of the structure and limit the excitation of stray surface waves. Some of these aspects are configured such that the thickness of the substrate layer is proportional to the pitch value of the fingers of the interdigital transducer. Some of these aspects are configured such that the AlN substrate layer is a single-crystal AlN layer.

[0012] Some of these aspects are configured such that the AlN substrate layer is a ceramic AlN layer. Some of these aspects are configured such that the AlN substrate layer is fabricated as a non-piezoelectric layer using ceramic materials and disordered polycrystalline AlN or amorphous AlN.

[0013] Some of these aspects are configured such that the AlN substrate layer is a deposited thin film layer. Some of these aspects are configured such that the AlN substrate layer is doped with scandium to adjust the velocity (v). sh The value is specified. In some aspects, an AlN layer and an AlScN layer are used, wherein the AlScN layer is located on the electrode side of the AlN layer, such that the AlScN is located between the AlN layer and the electrode layer. Some such aspects are configured such that the substrate layer further includes a glass support layer, wherein the AlN substrate layer is disposed between the piezoelectric layer and the glass support layer.

[0014] Some of these aspects are configured such that the substrate layer further includes a glass support layer, wherein the AlN substrate layer is disposed between the glass support layer and the piezoelectric layer. Some of these aspects are configured such that the glass support layer is doped to match the thermal expansion coefficient of the glass support layer with that of the piezoelectric layer. Some of these aspects are configured such that the glass support layer is formed of amorphous SiO2. Some of these aspects are configured such that the glass support layer is formed of crystalline SiO2.

[0015] Some of these aspects are configured such that the piezoelectric layer comprises lithium tantalate (LT), wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ). Some of these aspects are configured such that the µ value is in the range of -80° to -30°. Some of these aspects are configured such that the piezoelectric layer is in a configuration selected from LT0 to LT 60. Some of these aspects are configured such that the piezoelectric layer is in a configuration selected from LT25 to LT 50. Some of these aspects are configured such that the thickness of the piezoelectric layer is approximately 0.4 times the pitch value of the interdigital transducer fingers. Some of these aspects are configured such that the thickness of the piezoelectric layer is between 0.2 and 0.8 times the pitch value of the interdigital transducer fingers. Some of these aspects are configured such that the thickness of the AlN substrate layer is less than four times the pitch value.

[0016] Some of these aspects also include a SiO2 compensation layer located between the piezoelectric layer and the AlN substrate layer. Some of these aspects are configured such that the SiO2 compensation layer is approximately between 0.2 and 0.8 times the pitch value of the interdigital transducer fingers.

[0017] Some of these aspects are configured such that the piezoelectric layer comprises lithium tantalate, and the Euler angle is selected from the set of lithium tantalate Euler angles including LT15, ​​LT20, LT30, LT36, LT39, LT42, LT46.3 and LT50.

[0018] Some of these aspects are configured such that the piezoelectric layer and the interdigital transducer are configured to excite specific shear polarization wave modes.

[0019] This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to define the scope of the claimed subject matter. This subject matter should be understood with reference to the appropriate portions of the entire specification, any or all drawings, and each claim.

[0020] The foregoing, as well as other features and embodiments, will become more apparent upon reference to the following description, claims, and drawings. Attached Figure Description

[0021] Figure 1 Example operating environments for surface acoustic wave (SAW) resonators are illustrated according to the aspects described herein.

[0022] Figure 2 Example wireless transceivers, including filters implemented using SAW resonators, are illustrated according to the aspects described herein.

[0023] Figure 3 Various aspects of a SAW device are illustrated according to the aspects described herein.

[0024] Figure 4A and Figure 4B Example implementations of SAW resonators based on the aspects described herein are illustrated.

[0025] Figure 5 An example Euler angle is given for the orientation of the crystal structure of the piezoelectric material in a SAW resonator, as defined by the various aspects described herein.

[0026] Figure 6 Various aspects of a SAW device are illustrated according to the aspects described herein.

[0027] Figure 7 The graphs depict various example performance characteristics of SAW resonators with aluminum nitride layers, illustrating some of the aspects described herein.

[0028] Figure 8 Various aspects of a SAW device are illustrated according to the aspects described herein.

[0029] Figures 9A to 9B The graphs depict various example performance characteristics of SAW resonators with aluminum nitride layers, illustrating some of the aspects described herein.

[0030] Figure 10 Various aspects of a SAW device are illustrated according to the aspects described herein.

[0031] Figures 11A to 11D The graphs depict various example performance characteristics of SAW resonators with aluminum nitride layers, illustrating some of the aspects described herein.

[0032] Figure 12A and Figure 12B Examples of the use of SAW in wireless communication devices according to the aspects described herein are illustrated.

[0033] Figure 13A and Figure 13B Example implementations of SAW resonators based on the aspects described herein are illustrated.

[0034] Figure 14 This is a flowchart illustrating an example process for manufacturing a SAW resonator according to the aspects described herein. Detailed Implementation

[0035] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of exemplary embodiments and is not intended to represent the only specific embodiments in which the invention may be practiced. The detailed description includes specific details for the purpose of describing aspects of a surface acoustic wave (SAW) device having an aluminum nitride layer according to the aspects described herein, which in some aspects may be a thin-film SAW (TFSAW) device. Alternative aspects not specifically detailed are possible within the scope of the described aspects.

[0036] Electroacoustic devices (e.g., "acoustic filters") are used in many applications to filter high-frequency (e.g., typically greater than 100 MHz) signals. Acoustic filters are tuned to allow certain frequencies (e.g., frequencies within their passband) to pass through and reflect other frequencies (e.g., frequencies outside their passband). Using piezoelectric materials as the vibrating medium, acoustic filters operate by converting electrical signal waves propagating along an electrical conductor into sound waves (e.g., acoustic signal waves) formed on the piezoelectric material. The sound waves are then converted back into an electrically filtered signal.

[0037] Sound waves propagate across piezoelectric materials at a speed significantly slower than that of electromagnetic waves. Generally, the wave propagation speed v is proportional to the wave wavelength lambda and depends on the wave frequency f (e.g., where the speed v = lambda). f). Therefore, after converting an electrical signal wave into a sound wave, the wavelength of the sound wave is significantly smaller than the wavelength of the electrical signal wave. The resulting smaller wavelength of the sound 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.

[0038] Surface acoustic wave (SAW) resonators are designed to allow sound waves to propagate through a piezoelectric material in a specific direction (e.g., a dominant acoustic mode). However, various acoustic modes in other directions can be generated due to the properties of the specific piezoelectric material used and the way the piezoelectric material is excited by a signal interacting with the electrode structure. Electroacoustic devices with lithium tantalate (LT) or lithium niobate (LN) piezoelectric layers bonded to a silicon (Si) carrier silicon oxide (SiO2) layer are common for high-frequency acoustic filtering for wireless communication. However, such devices can have many trade-offs. Despite having high Q values ​​at room temperature and sufficient coupling for many RF bands, such devices can have wafer and device warping related to the thermal expansion mismatch between silicon and the piezoelectric material (e.g., a mismatch between the expansion coefficient of Si, which is around 2.6 parts per million (ppm / K), and the expansion coefficient of the example piezoelectric material, which is about 14-15 ppm / K). The thermal coefficient of frequency (TCF) can vary across a frequency range (e.g., for the resonant and anti-resonant frequencies of a resonator), and therefore, thermal variations at the upper and lower band edges of a filter can cause problems with filter operation at these thermal boundaries. Due to the semiconductor properties of silicon, the use of silicon substrates can additionally lead to passband breakdown at high power levels and / or higher temperatures.

[0039] The aspects described herein include improving device performance by incorporating aluminum nitride in the substrate layer compared to a silicon substrate, thereby utilizing better thermal matching between the piezoelectric layer and the substrate layer. Additionally, device performance at high power levels and / or high temperatures is improved by utilizing the AlN substrate layer to avoid the semiconductor characteristics of a silicon substrate.

[0040] In the example implementation, the thin-film surface acoustic wave filter includes an electrode structure, a substrate layer, and a piezoelectric layer. The substrate layer is formed using an AlN layer in the substrate and a piezoelectric layer having a crystal orientation defined by Euler angles lambda (λ), mu (µ), and theta (θ). The AlN substrate acts as a high-speed carrier layer to confine wave energy to surface modes and limit parasitic modes other than the dominant mode.

[0041] A single piezoelectric crystal is used in some filter resonators or wafer structures (e.g., wafers made of a single crystalline (bulk) material). The crystal orientation of the piezoelectric layer can be defined by Euler angles. Some crystal orientations (e.g., corresponding to a range of Euler angles) are more useful than others because they allow high excitation of only one mode, which has advantageous properties for filter operation. In some cases, the value of the Euler angle is defined for a given material, such as the Euler angles (0, -60, 0) for LT30YX (LT-lithium tantalate), the Euler angles (0, -48, 0) for LT42YX, or other Euler angles. In some aspects, the manufacturing tolerance of such angles can be a variation of less than 0.3 degrees. In some aspects, the piezoelectric layer is configured with selected Euler angles for exciting the primary shear polarization wave (e.g., on the LT or LN of the resonator) to achieve high electroacoustic coupling. In some aspects, specifically utilizing thick AlN layers (e.g., ceramic layers that can also be used as heat sinks), other Euler angles (e.g., piezoelectric shearing) can be used to excite Rayleigh waves. Such aspects can be targeted at the excitation of a single dominant mode (e.g., Rayleigh or shearing). Different Euler angle ranges can be used to select the mode.

[0042] The aspects described herein can utilize materials with grain orientations defined by various standard Euler angles, such as those used for lithium tantalate (LiTaO3 / LT) 15 (LT15), LT20, LT30, LT36, LT39, LT42, LT46.3, LT50, LT25, or other such angles. For thin-film SAW (TFSAW) devices, all LT cuts in which highly coupled shear waves are primarily excited can be used. Specific cuts can be selected for the design based on the layer thicknesses in the stack to optimize resonator or filter performance. In some aspects, the cut can be selected to suppress the excitation of unwanted Rayleigh waves for a given combination of layer thicknesses and frequency range. The corresponding LT cuts can be selected from LT10…LT50 (e.g., LTxx with angles of 10<~xx<~50 or other such angles). In some aspects, Euler angles can be intentionally modified to offset the mu (µ) angle away from the standard angles, thereby modifying and adjusting the excitation of parasitic modes and limiting resonant spikes in TFSAW resonator operation. In some aspects, the third angle θ can also be varied by rotating the photolithographic mask used during manufacturing to optimize operation for low loss in a specific implementation. This angle can also be varied directly during the fabrication of the single-crystal wafer, and a master notch can be created to identify this angle. In TFSAW structures, the design can also be chosen to rotate away from the direction marked by the master crystal axis of the AlN or Si carrier wafer.

[0043] Various aspects of this disclosure will be described with reference to the figures.

[0044] Figure 1An example environment 100 for wireless communication according to the aspects described herein is illustrated, comprising a device operating using a SAW substrate layer with an AlN substrate. 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, etc.

[0045] 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 tower in a cellular network, base station 104 can be represented or implemented as another device, such as a satellite, server equipment, terrestrial television broadcasting tower, access point, peer-to-peer device, mesh network node, fiber optic cable, etc. Therefore, computing device 102 can communicate with base station 104 or another device via wired connection, wireless connection, or a combination thereof.

[0046] 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, or 5G 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.

[0047] 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.

[0048] 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.

[0049] The wireless transceiver 120 of computing device 102 provides connectivity to a suitable network and other electronic devices connected thereto. Alternatively or additionally, computing device 102 may include a wired transceiver (such as an Ethernet or fiber optic interface) for communication over a local network, intranet, or the Internet. Wireless transceiver 120 can facilitate 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, wireless wide area network (WWAN), and / or wireless personal area network (WPAN). In the context of example environment 100, wireless transceiver 120 enables computing device 102 to communicate with base station 104 and the network connected thereto. However, wireless transceiver 120 can also enable computing device 102 to communicate "directly" with other devices or networks.

[0050] 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.

[0051] exist Figure 1 In the example shown, the wireless transceiver 120 includes at least one filter 124 having one or more SAW resonators 126 (e.g., TFSAW resonators) fabricated using an AlN substrate layer 128. In some aspects, the AlN substrate layer 128 is a carrier layer within a substrate along with glass (e.g., an amorphous silicon oxide layer). In some aspects, the glass support substrate layer is doped to match the coefficient of thermal expansion of other layers in the TFSAW resonator. In some aspects, a thin-film SiO2 layer may also be present to improve performance, as detailed below.

[0052] Figure 2 An 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 selectively connected to the same antenna via a switch (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 broadband filter 124-1. The receiver 204 includes at least one second broadband 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.

[0053] In some implementations, the wireless transceiver 120 is implemented using multiple 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, a broadband filter 124-1 for transmitter 202, a broadband filter 124-2 for receiver 204, and an amplifier 212 for receiver 204.

[0054] 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 spurious (e.g., 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 wideband filter 124-1. The first broadband 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 broadband filter 124-1 reduces one or more spurious 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.

[0055] During reception, antenna 122-2 receives radio frequency (RF) signal 228 and transmits it to receiver 204. Second bandwidth filter 124-2 receives the received RF signal 228, represented by pre-filtered received signal 230. The second bandwidth filter 124-2 filters any spurious frequencies within the pre-filtered received signal 230 to generate a filtered received signal 232. Examples of spurious frequencies may include interference from sources or noise from the external environment. Amplifier 212 of receiver 204 amplifies the filtered received signal 232 and transmits it to second mixer 208-2. Second mixer 208-2 down-converts the amplified filtered received signal 232 using a local oscillator signal 222 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. Wideband filters 124-1 and 124-2 can be implemented by one or more thin-film surface acoustic wave resonators 126, examples of which are further described below. Figure 3 Describe it.

[0056] Figure 3 Various aspects of a TFSAW stack of a thin-film surface acoustic wave resonator 126 are illustrated. In the depicted configuration, the thin-film surface acoustic wave resonator 126 includes at least one electrode structure 302, at least one piezoelectric layer 304 (e.g., a piezoelectric material), and at least one substrate layer 306. The electrode structure 302 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 metal layers and may optionally include one or more adhesive layers. As an example, the metal layers may be composed of aluminum (Al), copper (Cu), silver (Ag), gold (Au), tungsten (W), or some combination or doping form thereof. The adhesive layers may be composed of chromium (Cr), titanium (Ti), molybdenum (Mo), or some combination thereof.

[0057] Electrode structure 302 includes one or more interdigital transducers 308. The interdigital transducer 308 converts an electrical signal into an acoustic wave and the acoustic wave back into a filtered electrical signal. An interdigital transducer (IDT) converts an electrical signal into an acoustic wave and has a strong frequency-dependent admittance; therefore, the IDT is used as a basic structure for filtering. Some filters work with combinations of two or more IDTs, where one IDT excites a wave that is received and converted back by another IDT. Other filters use two or more IDTs with reflector fingers and may use only the combination of frequency-dependent admittance to filter the electrical signal. In some systems, multiple types of filtering combinations may exist in a single device. Thus, as described above, IDTs such as the interdigital transducer 308 convert electrical signals into acoustic waves and / or convert acoustic waves back into electrical signals.

[0058] The example interdigital transducer 308 is further described below. Although not explicitly shown, the electrode structure 302 may also include two or more reflectors. In the example embodiment, the interdigital transducer 308 is arranged between two reflectors that reflect sound waves back to the interdigital transducer 308.

[0059] The material of the piezoelectric layer 304 and the orientation of the propagation surface relative to the crystal structure of the material affect several performance parameters. Example performance parameters include the electroacoustic coupling factor (K). 2 The electroacoustic coupling factor (TCF) represents the frequency response, the mode or type of the generated sound wave, and / or the velocity of the sound wave. The electroacoustic coupling factor characterizes the efficiency of the thin-film surface acoustic wave resonator 126 in converting electrical energy to mechanical energy. Compared to another filter with a lower electroacoustic coupling factor, a filter with a higher electroacoustic coupling factor experiences less insertion loss and improved impedance matching over a wider frequency range. The frequency temperature coefficient characterizes the resonant frequency of the filter or the amount by which the filter skirt changes in response to temperature changes. Compared to another filter with a larger absolute value of the frequency temperature coefficient, a filter with a smaller absolute value of the frequency temperature coefficient has a more stable frequency response over a given temperature range.

[0060] The substrate layer 306 may include one or more sublayers that can support charge trapping, temperature compensation, power handling, mode suppression, etc. In some aspects, the substrate layer 306 may be formed as an AlN substrate, and the piezoelectric layer 304 may be formed on the top surface of the AlN substrate layer (e.g., as described below regarding...). Figure 6 (as described above). In other aspects, the AlN substrate layer 128 may be a sublayer with an additional glass support layer, and an optional SiO2 layer between the AlN substrate layer and the piezoelectric layer (e.g., LT). For certain specific implementations, this structure can provide waveguide operation to emphasize surface wave modes and reduce stray modes.

[0061] In some aspects, substrate layer 306 may include at least one compensation layer 312, at least one charge trapping layer 314, at least one support layer 316, or some combination thereof. These sublayers may be considered as part of substrate layer 306 or as separate layers on their own.

[0062] The compensation layer 312 provides temperature compensation, enabling the TFSAW resonator 126 to achieve a target frequency temperature coefficient based on the thickness of the material in the piezoelectric layer 304. In some embodiments, the thickness of the compensation layer 312 can be tailored to provide mode suppression (e.g., suppression of stray plate modes). In an example embodiment, the compensation layer 312 can be implemented as an AlN substrate layer 128. In other embodiments, SiO2 or SiOF (e.g., fluorine-doped SiO2) can be used as a material with inherent temperature compensation properties (e.g., hardened at higher temperatures).

[0063] The charge trapping layer 314 can suppress nonlinear substrate effects. The charge trapping layer 314 may include at least one polycrystalline silicon (poly-Si) layer (e.g., a polycrystalline silicon layer or a polycrystalline 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, or some combination thereof. In some aspects of the specific embodiments described herein, the charge trapping layer 314 is optional and may be absent in some designs.

[0064] The support layer 316 enables acoustic waves to form across the surface of the piezoelectric layer 304 and reduces the amount of energy leaking into the substrate layer 306. In some embodiments, the support layer 316 may also function as a compensation layer 312. Generally, the support layer 316 is made of a non-conductive material that provides isolation. For example, the support layer 316 may include at least one silicon (Si) layer (e.g., a doped high-resistivity silicon layer), at least one sapphire layer, at least one silicon carbide (SiC) layer, at least one fused silica layer, at least one glass layer, at least one diamond layer, or some combination thereof. In other aspects, the support layer 316 may be AlN or AlN and glass. In some embodiments, the support layer 316 has a coefficient of thermal expansion (TEC) relatively similar to that of the piezoelectric layer 304. The support layer 316 may have a specific crystal orientation to support the suppression or attenuation of stray modes, as further discussed below. Figure 5 As stated above.

[0065] Figure 4A and Figure 4B An exemplary embodiment of a TFSAW resonator 126 having an AlN substrate layer 306 on a piezoelectric layer 304 is illustrated. A three-dimensional perspective view 400 of the TFSAW resonator 126 is shown in... Figure 4A As shown in the figure, and in the two-dimensional cross-sectional view 402 of the TFSAW resonator 126 Figure 4BAs shown in the image.

[0066] In the configuration depicted in the two-dimensional cross-sectional view 402, the piezoelectric layer 304 is disposed between the electrode structure 302 and the substrate layer 306. Figure 4A A single AlN substrate layer is shown, but in some specific embodiments, substrate layer 306 may include sublayers as described above, such as compensation layer 312, charge trapping layer 314, and support layer 316, wherein the AlN substrate layer is as follows: Figure 6 , Figure 8 or Figure 10 As described herein, it is included. A compensation layer 312 is disposed between the piezoelectric layer 304 and the charge trapping layer 314. The charge trapping layer 314 is disposed between the compensation layer 312 and the support layer 316. The electrode structure 302 includes an interdigital transducer 308. Although in Figure 4A and Figure 4B Not explicitly shown, but electrode structure 302 may also include one or more other interdigital transducers 308 and two or more reflectors.

[0067] In the three-dimensional perspective view 400, the interdigital transducer 308 is shown having two comb-shaped electrode structures, wherein fingers extend from two busbars (e.g., conductive segments or tracks) toward each other. The electrode fingers are arranged in an interlocking manner between the two busbars of the interdigital transducer 308 (e.g., in an interdigital arrangement). In other words, fingers connected to the first busbar extend toward the second busbar but are not connected to the second busbar. Therefore, gaps exist between the ends of these fingers and the second busbar. Similarly, fingers connected to the second busbar extend toward the first busbar but are not connected to the first busbar. Therefore, gaps exist between the ends of these fingers and the first busbar.

[0068] Along the direction of the generatrix, there is an overlapping region, which includes a central region 404 in which a portion of one of the fingers overlaps with a portion of an adjacent finger. The overlapping central region 404 may be referred to as an aperture, track, or active region, in which an electric field is generated between the fingers to cause an acoustic wave 414 to be formed at least in this region of the piezoelectric layer 304.

[0069] The physical periodicity of the fingers is referred to as the pitch 406 of the interdigital transducer 308. The pitch 406 can be indicated in various ways. For example, in some aspects, the pitch 406 may correspond to a magnitude of the distance between consecutive fingers of the interdigital transducer 308 in the central region 404. For example, this distance may be defined as the distance between the center points of each finger in the fingers. When the fingers have a uniform width, this distance is typically measured between the right (or left) edge of one finger and the right (or left) edge of an adjacent finger. In some aspects, the average distance between adjacent fingers of the interdigital transducer 308 can be used for the pitch 406.

[0070] The frequency at which the piezoelectric layer 304 vibrates is the main resonant frequency of the stack of electrode structures 302, including the resonator 126 (e.g., as...). Figure 4A Illustrated from perspective view 400, the entire stack of resonators 126 extends from the surface downwards and into the AlN layer of the substrate to resonate. This frequency is determined at least in part by the pitch 406 of the interdigital transducer 308 and other properties of the thin-film surface acoustic wave resonator 126. As an example, the pitch 406 may be between approximately 0.30 micrometers (μm) and 0.45 micrometers to enable the thin-film surface acoustic wave resonator 126 to have a principal resonant frequency of approximately 5 GHz. Other pitches 406 may also achieve other principal resonant frequencies. Other example pitches 406 may be between approximately 0.3 µm and 3.0 µm. In various embodiments, the pitch 406 of a given embodiment may be matched with the thickness of the TFSAW resonator 126 layer. For example, the thickness of the substrate layer 306 or a given sublayer of the substrate layer 306 may be set as an approximate (e.g., limited by manufacturing variations) ratio of the pitch 406 to give a particular frequency performance.

[0071] In one aspect, the thickness of electrode structure 302 can be characterized by pitch 406. For example, the ratio of the thickness of electrode structure 302 to twice the pitch 406 can be approximately eight percent (e.g., hmet / 2 or approximately 0.08 or 8%, exemplified as 7.5% of (h / 2p), which in the example below is equal to 150 nm). Similarly, the thickness of piezoelectric layer 304 can also be characterized by pitch 406 of electrode structure 302. For example, the ratio of the thickness of AlN substrate layer can be four times the pitch 406 (e.g., twice the wavelength of the acoustic wave excited by IDT fingers). Likewise, the thickness of compensation layer 312 or any other layer in the TFSAW stack can be characterized by pitch 406 of electrode structure 302.

[0072] It should be understood that, although in Figure 4A and Figure 4B The illustration shows a certain number of fingers, 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 thin-film surface acoustic wave resonator 126 may include multiple interconnecting electrode structures, each including multiple interdigital transducers 308 to achieve a desired passband (e.g., multiple interconnecting resonators or interdigital transducers 308 connected in series or parallel to form a desired filter transfer function).

[0073] Although not shown, each reflector within electrode structure 302 may have two busbars and grating structures for conductive fingers, each connected to one of the two busbars. In some embodiments, the pitch of the reflector may be similar to or the same as the pitch 406 of the interdigital transducer 308 to reflect sound waves 414 within the resonant frequency range.

[0074] In the three-dimensional perspective view 400, the thin-film surface acoustic wave resonator 126 is defined by a first filter (X) axis 408, a second filter (Y) axis 410, and a third filter (Z) axis 412. The first filter axis 408 and the second filter axis 410 are parallel to the flat surface of the piezoelectric layer 304, and the second filter axis 410 is perpendicular to the first filter axis 408. The third filter axis 412 is orthogonal (e.g., perpendicular) to the flat surface of the piezoelectric layer 304. The generatrix of the interdigital transducer 308 is oriented parallel to the first filter axis 408. The fingers of the interdigital transducer 308 are oriented parallel to the second filter axis 410. Furthermore, the orientation of the piezoelectric layer 304 causes acoustic waves 414 to form primarily in the direction of the first axis 408. Therefore, acoustic waves 414 are formed in a direction substantially perpendicular to the direction of the fingers of the interdigital transducer 308.

[0075] The acoustic wave 414 can be, for example, a shear-polarized wave. Shear-polarized waves enable the thin-film surface acoustic wave resonator 126 to achieve high electroacoustic coupling.

[0076] During operation, the thin-film surface acoustic wave resonator 126 receives radio frequency signals, such as... Figure 2 The pre-filter transmit signal 224 or pre-filter receive signal 230 is shown. Electrode structure 302 uses the inverse piezoelectric effect to excite acoustic waves 414 on piezoelectric layer 304. For example, interdigital transducers 308 in electrode structure 302 generate an alternating electric field based on the received radio frequency signal. Piezoelectric layer 304 is formed to enable acoustic waves 414 to respond to this alternating electric field generated by interdigital transducers 308. In other words, piezoelectric layer 304 is formed at least partially to enable acoustic waves 414 to respond to electrical stimulation by one or more interdigital transducers 308.

[0077] Sound wave 414 propagates across piezoelectric layer 304 and interacts with interdigital transducer 308 or another interdigital transducer within electrode structure 302. Figure 4A or Figure 4B (Not shown in the image) interact. The propagating sound wave 414 can be a standing wave. In some embodiments, two reflectors within the electrode structure 302 cause the sound wave 414 to be formed as a standing wave across a portion of the piezoelectric layer 304. In other embodiments, the sound wave 414 propagates across the piezoelectric layer 304 from one interdigital transducer 308 to another interdigital transducer.

[0078] Using the piezoelectric effect, electrode structure 302 is used, as described above, to filter the radio frequency (RF) signal associated with the propagating surface acoustic wave 414. Specifically, the piezoelectric layer 304 generates an alternating electric field due to the mechanical stress generated by the propagation of the acoustic wave 414. This alternating electric field induces an alternating current in another interdigital transducer (or interdigital transducer 308). This alternating current forms the filtered RF signal provided at the output of the thin-film RF resonator 126. In some aspects, the resonator may have multiple electrical ports or a single port described by an admittance value. The filtered RF signal may include... Figure 2 The filtered transmitted signal 226 or the filtered received signal 232.

[0079] Figure 5 The orientation of the piezoelectric material crystal structure in the piezoelectric layer 304 of the TFSAW resonator 126 is illustrated. Figure 3 Example Euler angle 310. A first crystal (X') axis 502, a second crystal (Y') axis 504, and a third crystal (Z') axis 506 are fixed along the crystal axis of the crystal (e.g., LT). A first rotation 500-1 is applied to rotate the first crystal X' axis 502 and the second crystal Y' axis 504 about the third crystal Z' axis 506. Specifically, the first rotation 500-1 rotates the first crystal X' axis 502 in the direction of the second crystal Y' axis 504. The angle associated with the first rotation 500-1 represents one Euler angle in Euler angle 310, which is denoted by the Euler angle lambda (λ) 508. The resulting rotation axes are represented by a new set of axes: X'' axis 510, Y'' axis 512, and Z'' axis 514. Figure 5 As shown, the third crystallization Z' axis 506 remains unchanged through the first rotation 500-1, making the third crystallization Z' axis 506 equal to the Z'' axis 514.

[0080] In the second rotation 500-2, the Y'' axis 512 and Z'' axis 514 are rotated about the X'' axis 510 by another Euler angle 310, which is represented by the Euler angle mu (µ) 518. In this case, the Y'' axis 512 is rotated in the direction of the Z'' axis 514. The resulting rotation axes are represented by a new set of axes: X''' axis 520, Y''' axis 522, and Z''' axis 524. Figure 5 As shown, the X'' axis 510 remains unchanged by the second rotation 500-2, making the X'' axis 510 equal to the X''' axis 520.

[0081] In the third rotation 500-3, the X''' axis 520 and the Y''' axis 522 are rotated about the Z''' axis 524 by an additional Euler angle 310, which is represented by the Euler angle theta (θ) 526. In this case, the X''' axis 520 is rotated in the direction of the Y''' axis 522. The resulting axis of rotation is determined by... Figure 4A and Figure 4B The filter axes (e.g., the first filter X-axis 408, the second filter Y-axis 410, and the third filter Z-axis 412) are used to represent this. Figure 5 As shown, the Z''' axis 524 remains unchanged by the third rotation 500-3, making the Z''' axis 524 equal to the third filter Z-axis 412. The X-axis 408 specifies the formation direction of the sound wave 414.

[0082] As described above, any number of standard Euler angles can be used in the aspects described herein, such as those used for lithium tantalate (LiTaO3 / LT) 15, LT20, LT30, LT36, LT39, LT42, LT46.3, LT50, LT25, etc. In some aspects as indicated above, the corresponding LT cut can be selected from LT10…LT50, or LTxx where 10 is less than xx and xx is less than approximately 50 (e.g., 10 ≤ ~xx ≤ ~50). In some aspects, the Euler angles can be intentionally modified to offset the mu (µ) angle away from the standard angle, thereby modifying and adjusting the excitation of parasitic modes and limiting resonant spikes in the operation of the TFSAW resonator. In some aspects, the third angle θ can also be varied by rotating the photolithographic mask used during manufacturing to optimize operation for low loss in a particular implementation. Generally speaking, the variation of any Euler angle in Euler angle 310 can be set by a given manufacturing process tolerance, and this variation can be less than or equal to + / - 1.5° in some respects, and less than or equal to + / - 0.2° in others. Therefore, the term approximately can mean that any Euler angle in Euler angle 310 is within + / - 1.5° of a specified value or less (e.g., within + / - 0.2° of a specified value).

[0083] exist Figure 4A In this context, the orientations of the first filter X-axis 408, the second filter Y-axis 410, and the third filter Z-axis 412 relative to the substrate layer (e.g., an AlN layer that can be used to implement the support layer 316) can be similarly defined by other Euler angles.

[0084] Figure 6Various aspects of a TFSAW resonator 600 according to the aspects described herein are illustrated. The TFSAW resonator 600 may be a specific implementation of the TFSAW resonator 126 discussed above. The TFSAW resonator 600 includes an electrode structure 602 comprising an interdigital transducer 608 having associated pitch characteristics defined by the space between the fingers of the IDT 608. The IDT 608 is positioned on top of a piezoelectric layer 604, which may be an LT layer, an LN layer, or any other suitable piezoelectric layer having resonant characteristics associated with Euler angles as described above, and is configured for excitation of surface thin-film modes and suppression of spurious modes of resonator operation to support a given wireless communication frequency band. The piezoelectric layer is positioned on top of an AlN substrate layer 612. AlN substrate layer 612 operates as a fast layer to keep the electroacoustic waves primarily confined to piezoelectric layer 604 (e.g., LT layer) and limit stray (e.g., leakage) modes of the electroacoustic waves of TFSAW resonator 600.

[0085] The AlN substrate layer 612 can be formed from a single-crystal AlN structure, a deposited film AlN structure, or a ceramic AlN structure. The properties of the TFSAW will depend on the properties of the AlN substrate layer, which can vary considerably depending on the AlN structure and the configuration of the piezoelectric layer 604. In some respects, this fabrication flexibility can provide for improvements in equipment related to device manufacturing. For example, existing deposition techniques for bulk acoustic wave (BAW) resonators can be used in some respects for the deposition of AlN substrate layers.

[0086]

[0087] Table 1

[0088] Table 1 above illustrates example properties of AlN structures that can be used in AlN substrate layer 612. Table 1 includes details of amorphous AlN layers, polystructured AlN layers, crystalline AlN structures, and two possible ceramic AlN structures. The expected properties shown illustrate sufficiently high volumetric wave initiation (e.g., Vsh around 5300 m / s–6200 m / s). As illustrated, the high initiation stiffness ceramic structure exhibits a relatively high Young's modulus (E) value (e.g., in the bottom two rows), resulting in a significantly higher wave velocity (Vsh) compared to other AlN structures. With the lower velocity provided by amorphous AlN, a 500 nm LT piezoelectric layer 604 can be used with an amorphous AlN substrate layer 612 at a thickness of several micrometers to generate a resonator response with acceptable stray properties.

[0089] While Table 1 and examples in this paper describe AlN structures, other structures are possible within the context of the aspects described herein. For example, in some aspects, aluminum scandium nitride (AlScN) or doped AlScN can be used instead of the AlN structure, or in addition to the AlN structure, aluminum scandium nitride (AlScN) or doped AlScN can be used. Such AlScN structures can operate, for example, with Vsh values ​​in the range of approximately 5400 m / s, thus providing benefits comparable to those of the AlN aspects described herein.

[0090] Figure 7 Examples are described Figure 6 Graph 700 illustrates various example performance characteristics of specific implementations of the TFSAW resonator 600, thus illustrating the impact of design variations of the TFSAW with an aluminum nitride layer according to the aspects described herein. Graph 700 illustrates the presence of two spurious modes (e.g., a Rayleigh mode slightly below the main resonance and another spurious mode at approximately 3 GHz), which are significantly affected by changing the Euler angle of LT in the TFSAW structure with AlN. Figure 7 The results are shown for 350 nm LT, 1.0 µm pitch, metallization ratio η=0.55 and hmet=150 nm.

[0091] Figure 7 and Figure 9A , Figure 9B and Figures 11A to 11D Simulation examples of admittance for different LT cuts for a resonator structure with a 1µm pitch and a 350nm LT piezoelectric thickness are shown together. These figures illustrate how the design can select the LT cut to minimize spurious emissions below resonance (e.g., LT~42) or to reduce the 3GHz spike.

[0092] Figure 8 Various aspects of a TFSAW device 800 according to the aspects described herein are illustrated. The TFSAW device 800 may be a specific implementation of the TFSAW resonator 126 discussed above. The TFSAW device 800 includes an electrode structure 802 comprising an interdigital transducer 808 having an associated pitch 806 characteristic defined by the space between the fingers of the IDT 808. The IDT 808 is disposed over a piezoelectric layer 804, which may be an LT layer, an LN layer, or any other suitable piezoelectric layer having resonant characteristics associated with the Euler angles as described above, and is configured for excitation of surface thin-film modes and suppression of spurious modes of resonator operation to support a given wireless communication frequency band. The piezoelectric layer 804 is located in a layer above an AlN substrate layer 814. In some aspects, as described below... Figure 10As described above, an optional SiO2 layer is positioned between the AlN substrate layer 814 and the piezoelectric layer 804. In other respects, the piezoelectric layer 804 is positioned directly on the surface of the AlN substrate layer 814, such as... Figure 8 exemplified.

[0093] Similar to the description above, the AlN substrate layer 814 operates as a fast layer, which keeps the electroacoustic waves confined to the piezoelectric layer 804. Therefore, the AlN substrate limits leakage into parasitic modes that cause unwanted spurious emissions and signal loss for the selected wireless communication frequency band.

[0094] exist Figure 8 In the example, the AlN substrate layer 814 is positioned on the glass support layer 816. In other aspects, the glass support layer 816 can be any suitable support layer configured as a support for the AlN substrate layer 814. In some aspects, instead of glass, a ceramic AlN layer can be used as the support, or the entire support and AlN substrate layer 814 can be combined into a single bulk AlN layer (e.g., similar to the one above). Figure 6 As described herein, the coefficient of thermal expansion (CTE) of the glass support substrate (e.g., parts per million of temperature change per Kelvin or Celsius) can be selected through glass doping or specific fabrication. As noted above, this provides a specific CTE that matches the piezoelectric or other layers of the TFSAW stack to deliver stable performance under high-power and / or high-temperature operating conditions. Specifically, mismatched CTEs in the TFSAW stack can cause bending or size misalignment of the TFSAW. This bending or device misalignment can alter the pitch of the IDT electrode fingers, resulting in device performance deviations that are dependent on the IDT pitch, as detailed herein. Furthermore, glass can provide fabrication benefits associated with larger wafer sizes, lower costs, and other such device benefits. For example, six-inch glass wafers can be used for TFSAW fabrication at a significantly lower cost than other support substrate materials that are only available in smaller wafer sizes.

[0095] Figure 9A and Figure 9B Examples are described Figure 8Graphs 900A and 900B illustrate various example performance characteristics of specific implementations of the TFSAW resonator device 800, thereby demonstrating the impact of design variations of a TFSAW with an aluminum nitride layer according to the aspects described herein. Graphs 900A and 900B illustrate aspects implemented according to the aspects described herein using a piezoelectric layer made of LT with a 42-rotYX cut (LT42) Euler angle, an electrode layer with a 1-micron (µm) pitch, and a 3-micron amorphous AlN layer as an AlN substrate layer. The line in graph 900A illustrates frequency operation for piezoelectric layer thicknesses varying from 200 nm to 700 nm. The illustrated graph 900A shows the main resonance near 2 GHz. Graph 900B shows the coupling value (K) plotted relative to the piezoelectric layer thickness. 2 In some respects, the highest possible coupling value is preferred, and graph 900B shows the highest coupling performance when the piezoelectric layer is larger than approximately 400 nanometers.

[0096] As described herein, layer thickness will depend on the relative geometry such that as the interdigital transducer (IDT) pitch changes, the relative thickness of other layers (e.g., piezoelectric layers) will change proportionally to achieve similar performance. According to curves 900A to 900B, in some respects, piezoelectric layers on AlN substrates will have a thickness greater than 0.4 times the IDT pitch to obtain acceptable performance.

[0097] In the illustrated plot 900A, the admittance curves show the simulation of LT42 on a 3-micrometer (µm) thick AlN, on a structure without SiO2, and on glass, as a function of the piezoelectric layer thickness, and the associated electroacoustic coupling. Plot 900B shows the k-axis plotted relative to the piezoelectric layer thickness. 2 Values. In some respects, for p=1µm, a piezoelectric thickness of at least about 400nm is required for the target resonator performance. Additional spurious modes occur at higher frequencies due to the thicker piezoelectric layer, as shown in graph 900A from 4GHz to 4.5GHz. Graph 900B illustrates high k values ​​for piezoelectric layer thicknesses of 400nm and above. 2 The benefit is that it increases the value, but for thicker voltage layers, the slightly higher k-value is less. 2 The benefits of the value are outweighed by the disadvantages of additional stray modes caused by the thicker piezoelectric layer.

[0098] Figure 10Various aspects of a TFSAW device 1000 according to the aspects described herein are illustrated. The TFSAW device 1000 may be a specific implementation of the TFSAW resonator 126 discussed above. The TFSAW device 1000 includes an electrode structure 1002 comprising an interdigital transducer 1008 having an associated pitch 1006 characteristic defined by the space between the fingers of the IDT 1008. The IDT 1008 is positioned on top of a piezoelectric layer 1004, which may be an LT layer, an LN layer, or any other suitable piezoelectric layer having resonant characteristics associated with the Euler angles as described above, and is configured for excitation of surface thin-film modes and suppression of spurious modes of resonator operation to support a given wireless communication frequency band. The piezoelectric layer 1004 is positioned in a layer above an AlN substrate layer 1014. Figure 10 In the example, the SiO2 layer 1012 is positioned between the AlN substrate layer 1014 and the piezoelectric layer 1004. In other respects, the piezoelectric layer 1004 is positioned directly on the surface of the AlN substrate layer 1014.

[0099] Similar to the description above, the AlN substrate layer 1014 operates as a fast layer, which keeps the electroacoustic waves confined to the piezoelectric layer 1004 and the SiO2 layer 1012. Therefore, the AlN substrate limits leakage into parasitic modes that cause unwanted spurious emissions and signal loss for the selected wireless communication frequency band.

[0100] exist Figure 10 In the example, the AlN substrate layer 1014 is positioned on the glass support layer 1016. In some aspects, the glass support layer 1016 may be amorphous SiO2. In other aspects, the glass support layer 1016 may be any suitable support layer configured as a support for the AlN substrate layer 1014. In some aspects, instead of glass, a ceramic AlN layer may be used as the support, or the entire support and the AlN substrate layer 1014 may be combined into a single bulk AlN layer (e.g., similar to the one above). Figure 6 ).

[0101] Figure 11A and Figure 11B Examples are described Figure 10Graphs 1100A and 1100B illustrate various illustrative performance characteristics of specific implementations of the TFSAW resonator device 1000, thereby demonstrating the impact of design variations of a TFSAW with an aluminum nitride layer according to the aspects described herein. Graphs 1100A and 1100B illustrate aspects implemented according to the aspects described herein using a piezoelectric layer made of LT with a 30-rot YX cut, an electrode layer with a 1-micron (µm) pitch, a 500-nanometer SiO2 layer, and a 3-micron amorphous AlN layer as an AlN substrate layer. The line in Graph 1100A illustrates frequency operation for the piezoelectric layer varying from 200 nm to 600 nm. The illustrated graph 1100A shows the main resonance near 2 GHz, and the static capacitance Cs is lower for smaller piezoelectric layers. Figure 1100A also shows the influence of Cs on the filter structure size, where higher Cs values ​​result in improved performance, leading to a performance trade-off between additional spurious emissions and the improved performance associated with higher Cs values.

[0102] Figure 1100B shows the coupling value (K) plotted relative to the piezoelectric layer thickness. 2 In some respects, the highest possible coupling value is preferred, and graph 1100B shows the highest coupling performance when the piezoelectric layer is between approximately 300 nm and 400 nm.

[0103] Figure 11C Plot 1100C shows the frequency response characteristics of another specific implementation utilizing an LT30, 1µm pitch, 500nm SiO2 layer, and 400nm piezoelectric layer, corresponding to the details in plots 1100A to 1100B above. Figure 11C In Figure 1100C, the frequency response characteristics are shown as the AlN substrate layer thickness varies from 2.5 μm to 5 μm. Figure 1100C includes a stray region 1100D, where the AlN thickness affects the stray peaks in the stray region 1100D. Furthermore, Figure 1100C illustrates the maximum k-value when the AlN thickness varies, where p = 1 µm. 2 Simulation results of the structure. AlN thickness has a small impact on the master mode, but a certain impact on stray modes, such as... Figure 11D exemplified.

[0104] Figure 11DThe spurious region 1100D of graph 1100C is shown in magnified form. As illustrated, at AlN substrate thicknesses greater than 4 μm, a large peak occurs at approximately 2.6 GHz, while the peak near 2.9 GHz slightly contracts. In some respects, due to the smaller spurious emissions at 2.6 GHz and the relatively similar size of spurious emissions at 2.9 GHz, the AlN substrate layer according to the details of the specific implementation above will operate with improved performance at AlN substrate thicknesses less than 3.5 μm.

[0105] As indicated above, the layer thickness will depend on the relative geometry such that as the interdigital transducer (IDT) pitch changes, the relative thickness of other layers (e.g., piezoelectric layers) will change proportionally to achieve similar performance. According to graphs 1100A to 1100D, in some respects, the piezoelectric layer on the AlN substrate will have a thickness of approximately 0.3 to 0.4 times the IDT pitch, and the AlN substrate will have a thickness of less than 3.5 times the IDT pitch.

[0106] The above examples describe a specific implementation of a TFSAW resonator using an AlN substrate layer. As described herein, other TFSAW resonators with an AlN substrate layer are possible. For example, while the performance of lithium tantalate (LiTaO3 / LT) at a specific Euler angle has been described, other piezoelectric materials and other Euler angles can be used in some aspects. For example, in some aspects, LT15, ​​LT20, LT25, LT30, LT36, LT39, LT42, LT46.3, or LT50 may be used. For each such material and material configuration, corresponding thicknesses of different layers including the AlN substrate layer can be selected for the corresponding performance characteristics associated with a particular application. The above description uses, for example, LT30 as a shorthand for lithium tantalate at Euler angles (0, -60, 0). Such angles have the equivalent angles as described above. Additionally, based on manufacturing variations or other design variations, the Euler angles for the third angle may vary within approximately 1 degree, within 5 or 10 degrees, or other such ranges. Similarly, any angle can be adjusted based on the specific design characteristics required for a particular application.

[0107] According to the aspects described herein, thin-film (TF) SAW resonators are sensitive to Euler angle configuration. In a TFSAW resonator, shear-polarized waves can be excited and propagate at the surface of the structure. If the constraint (e.g., fast) layer beneath the piezoelectric layer is not properly selected, the wave can suffer losses, which affects the Q value of the TFSAW resonator. Using TFSAW structures, losses entering the bulk support material can be suppressed over certain frequency ranges, down to the volume wave initiation frequency of the carrier structure (e.g., Vsh). According to the aspects described herein, this can be the Vsh of the AlN substrate layer.

[0108] Figure 12AThis is a schematic diagram of an electroacoustic filter circuit 1200 comprising one or more TFSAW resonators (e.g., to implement a filter for wireless communication signals) having an AlN substrate layer, according to various aspects described herein. Figure 12A Examples include a trapezoidal structure. Other structures may be used in other examples. Filter circuit 1200 provides an example in which a TFSAW resonator with an AlN substrate layer according to the aspects described herein provides improved performance due to improved thermal performance and high power performance, as well as lower cost and manufacturing improvements as described above. Filter circuit 1200 has an input terminal 1202 and an output terminal 1216. A trapezoidal network of resonators is provided between the input terminal 1202 and the output terminal 1216. The resonators may be SAW resonators or any other such resonator devices as detailed herein (e.g., BAW, etc.), including at least one TFSAW resonator with an AlN substrate layer according to the aspects described herein. Filter circuit 1200 includes a first resonator 1204, a second resonator 1206, a third resonator 1208, and a fourth resonator 1209, all of which are electrically connected in series between the input terminal 1202 and the output terminal 1216. The fifth resonator 1210 (e.g., a shunt resonator) has a first terminal connected between the first resonator 1204 and the second resonator 1206, and a second terminal connected to ground potential. The fifth resonator 1212 (e.g., a shunt resonator) has a first terminal connected between the second resonator 1206 and the third resonator 1208, and a second terminal connected to ground potential. Similarly, the seventh resonator 1214 has a first terminal connected between the third resonator 1208 and the fourth resonator 1209, and a second terminal connected to ground potential (e.g., directly, or using additional circuitry such as an inductor or other connection circuitry coupled to ground potential). The electroacoustic filter circuit 1200 may, for example, be a bandpass circuit having a passband within a selected frequency range (e.g., approximately between 100 MHz and 3.5 GHz).

[0109] Figure 12B This is a schematic diagram of a multiplexer circuit 1250 with multiple filters configured for multi-band communication using antenna node 1280. The filters include those from... Figure 12AThe filter circuit 1200 includes an output terminal 1216 and an input terminal 1202. Additional filters 1252, 1254, 1256, 1258, 1260, and 1262 are shown; these additional filters can be used in corresponding frequency bands of a multi-band communication system. Other examples may include multiplexing with any number of filters. When the frequency band associated with filters 1260 and 1262 is not used, switch 1290 can isolate filters 1260 and 1262 from the remaining filters. When filters 1260 and 1262 are not used, the isolation filters 1260 and 1262 can improve the communication performance of the multiplexer circuit 1250 by limiting interference from filters 1260 and 1262 to signals from filters (or filter circuits) 1200-1258 (e.g., when filters 1260 and 1262 are disconnected by the switch, signal loss due to leakage into filters 1260 and 1262 is limited). Other examples may include additional switches to create additional groups of filters that can be isolated by these switches. Further examples may exclude switches, allowing all filters to be hardwired at the antenna nodes as part of the multiplexer circuitry.

[0110] Figure 13A This is a high-level top view representation of an example of the electrode structure 1304a of an electroacoustic device. Figure 13A and Figure 13B Provided in Figure 4A and Figure 4B The details of the reflector are briefly described but not shown. Figure 13A and Figure 13B The structure can be used to implement additional aspects of a TFSAW resonator (e.g., TFSAW resonator 126) with an AlN substrate layer as described herein. Electrode structure 1304a has an IDT 1305, which includes a first busbar 1322 (e.g., a first conductive segment or conductive trunk) electrically connected to a first terminal 1320 and a second busbar 1324 (e.g., a second conductive segment or conductive trunk) spaced apart from the first busbar 1322 and connected to a second terminal 1330. A plurality of conductive fingers 1326 are interdigitatedly connected to the first busbar 1322 or the second busbar 1324. The fingers 1326 connected to the first busbar 1322 extend toward the second busbar 1324 but are not connected to the second busbar 1324, such that a small gap exists between the ends of these fingers 1326 and the second busbar 1324. Similarly, the fingers 1326 connected to the second busbar 1324 extend toward the first busbar 1322 but are not connected to the first busbar 1322, such that there is a small gap between the ends of these fingers 1326 and the first busbar 1322.

[0111] Along the direction of the generatrix, there exists an overlapping region comprising a central region where a portion of one of the fingers overlaps with a portion of an adjacent finger, as illustrated by central region 1325. This overlapping central region 1325 may be referred to as an aperture, track, or active region, where an electric field is generated between the fingers 1326 to allow sound waves to propagate in this region of the piezoelectric layer. The periodicity of the fingers 1326 is referred to as the pitch of the IDT. The pitch can be indicated in various ways. For example, in some aspects, the pitch may correspond to the magnitude of the distance between the fingers in central region 1325. This distance may be defined, for example, as the distance between the center points of each of these fingers (and when the fingers have a uniform thickness, it is typically measured between the right (or left) edge of one finger and the right (or left) edge of an adjacent finger). In some aspects, the average distance between adjacent fingers can be used as the pitch. The frequency of the piezoelectric material's vibration is the self-resonant (also called "master resonance") frequency of the electrode structure 1304a. This frequency is determined at least in part by the pitch of the IDT 1305 and other properties of the electroacoustic device.

[0112] An IDT 1305 is arranged between two reflectors 1328 that reflect sound waves toward the IDT 1305 so that the sound waves are converted into electrical signals via the IDT 1305 in the illustrated configuration, and losses are prevented (e.g., the sound waves are confined and prevented from escaping). Each reflector 1328 has two busbars and a grid structure of conductive fingers, each connected to one of the two busbars. The pitch of the reflectors may be similar to or the same as the pitch of the IDT 1305 to reflect sound waves within the resonant frequency range. However, many configurations are possible.

[0113] Multiple electrode structures are possible. Figure 13A A single-port configuration can be broadly illustrated. Other configurations with multiple ports are also possible, as described herein. For example, electrode structure 1304a may have an input IDT 1305, where each terminal 1320 and 1330 serves as an input terminal. In this case, an adjacent output IDT (not illustrated) positioned between reflectors 1328 and adjacent to the input IDT 1305 can be provided to convert acoustic waves propagating in the piezoelectric layer into electrical signals to be provided at the output terminals of the output IDT.

[0114] Figure 13B This is a top-view view of another example of an electrode structure 1304b for an electroacoustic device. In this case, a dual-mode SAW (DMS) electrode structure 1304b is illustrated, which is a structure capable of inducing multiple resonances. Electrode structure 1304b includes multiple IDTs connected as illustrated, and a reflector 1328. Electrode structure 1304b is provided to illustrate various electrode structures to which the principles described herein are applicable, including... Figure 13A Electrode structure 1304a and Figure 13B The electrode structure is 1304b.

[0115] It should be understood that although a certain number of fingers 1326 are illustrated, the actual number of fingers, as well as the length and width of the fingers 1326 and the busbar, may differ in actual implementations. These parameters depend on the specific application of the filter and the desired frequency. Furthermore, the SAW filter may include multiple interconnect electrode structures, each including multiple IDTs to achieve the desired passband (e.g., multiple interconnect resonators or IDTs to form the desired filter transfer function).

[0116] Figure 14 This is a flowchart illustrating an example process 1400 for manufacturing a TFSAW resonator (e.g., TFSAW resonator 126). Process 1400 is described in the form of a set of boxes specifying operable operations. However, the operations are not necessarily limited to... Figure 14 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 fully or partially overlapping. Furthermore, more, fewer, and / or different operations can be implemented to perform process 1400 or alternative processes.

[0117] Process 1400 includes block 1402, which includes forming a substrate layer comprising an aluminum nitride (AlN) substrate layer. Process 1400 also includes block 1404, which includes forming a piezoelectric layer on a top surface of the substrate layer, wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ). Process 1400 also includes block 1406, which includes forming an electrode layer on the top surface of the piezoelectric layer, wherein the substrate layer and the piezoelectric layer are configured for surface wave excitation, and wherein the AlN substrate layer is configured as a fast layer to confine stray wave excitation. Although the blocks above are illustrated in a specific order, process 1400 may include intermediate blocks, steps, or operations. Furthermore, blocks that allow the fabrication of any structure described herein or elements of a resonator configured according to the description herein may be part of a specific implementation of process 1400.

[0118] Claim language or other languages ​​that state "at least one of" and / or "one or more of" in a set indicate that one member of the set or multiple members of the set (in any combination) satisfy the claim. For example, claim language stating "at least one of A and B" or "at least one of A or B" means A, B, or A and B. In another example, claim language stating "at least one of A, B, and C" or "at least one of A, B, or C" means A, B, C, or A and B, or A and C, or B and C, A and B and C, or any repeating information or data (e.g., A and A, B and B, C and C, A and A and B, etc.), or any other ordering, repetition, or combination of A, B, and C. The language "at least one of" and / or "one or more of" in a set does not limit the set to the items listed in the set. For example, the language of a claim stating "at least one of A and B" or "at least one of A or B" may refer to A, B, or A and B, and may additionally include items not listed in the set of A and B. The phrases "at least one" and "one or more" are used interchangeably herein.

[0119] Claims using phrases such as "at least one processor, configured to," "at least one processor configured to," "one or more processors, configured to," or "one or more processors configured to," or other languages, indicate that one or more processors (in any combination) are capable of performing associated operations. For example, the statement "at least one processor, configured to: X, Y, and Z" means that a single processor can be used to perform operations X, Y, and Z, or that multiple processors are each assigned a subset of the tasks of operations X, Y, and Z, such that multiple processors together perform X, Y, and Z, or that a group of multiple processors works together to perform operations X, Y, and Z. In another example, the claim language stating "at least one processor, configured to: X, Y, and Z" could mean that any single processor can perform only at least one subset of operations X, Y, and Z.

[0120] When referring to one or more elements that perform functions (e.g., steps of a method), one element may perform all functions, or more than one element may jointly perform these functions. When more than one element jointly performs these functions, each function does not need to be performed by every single element (e.g., different functions may be performed by different elements), and / or each function does not need to be performed by only one element as a whole (e.g., different elements may perform different sub-functions of a function). Similarly, when referring to one or more elements configured to cause another element (e.g., a device) to perform functions, one element may be configured to cause another element to perform all functions, or more than one element may be jointly configured to cause another element to perform these functions.

[0121] When referring to an entity that performs or is configured to perform functions (e.g., steps of a method) (e.g., any entity or device described herein), the entity may be configured to cause one or more elements (individually or collectively) to perform those functions. One or more components of the entity may include at least one memory, at least one processor, at least one communication interface, another component configured to perform one or more of those functions, and / or any combination thereof. When referring to an entity that performs functions, the entity may be configured to cause one component to perform all functions, or to cause more than one component to perform those functions collectively. When the entity is configured to cause more than one component to perform those functions collectively, each function does not need to be performed by every single component (e.g., different functions may be performed by different components), and / or each function does not need to be performed by only one component as a whole (e.g., different components may perform different sub-functions of a function).

[0122] The following is a set of non-limiting aspects based on the details provided herein: Aspect 1. A surface acoustic wave (SAW) resonator, the SAW resonator comprising: a substrate layer comprising an aluminum nitride (AlN) substrate layer; an electrode structure comprising an interdigital transducer; and a piezoelectric layer disposed between the electrode structure and the substrate layer.

[0123] Aspect 2. The SAW resonator according to Aspect 1, wherein the substrate layer and the piezoelectric layer are configured for surface wave excitation, and wherein the AlN substrate layer is configured as a fast layer to confine wave energy to the top of the structure and limit the excitation of stray surface waves.

[0124] Aspect 3. The SAW resonator according to any one of Aspects 1 to 2, wherein the thickness of the substrate layer is proportional to the pitch value of the fingers of the interdigital transducer.

[0125] Aspect 4. The SAW resonator according to any one of Aspects 1 to 3, wherein the AlN substrate layer is a single-crystal AlN layer.

[0126] Aspect 5. The SAW resonator according to any one of Aspects 1 to 3, wherein the AlN substrate layer is a ceramic AlN layer.

[0127] Aspect 6. The SAW resonator according to any one of Aspects 1 to 5, wherein the AlN substrate layer is fabricated as a non-piezoelectric layer using a ceramic material and disordered polycrystalline AlN or amorphous AlN.

[0128] Aspect 7. The SAW resonator according to any one of Aspects 1 to 6, wherein the AlN substrate layer is a deposited thin film layer.

[0129] Aspect 8. The SAW resonator according to aspect 7, wherein the AlN substrate layer is configured to adjust the speed (v) sh Scandium-doped thin film layer with a value of )

[0130] Aspect 9. The SAW resonator according to any one of Aspects 7 to 8, wherein the substrate layer further comprises a glass support layer, wherein the AlN substrate layer is disposed between the piezoelectric layer and the glass support layer.

[0131] Aspect 10. The SAW resonator according to any one of Aspects 1 to 6, wherein the substrate layer further comprises a glass support layer, wherein the AlN substrate layer is disposed between the glass support layer and the piezoelectric layer.

[0132] Aspect 11. The SAW resonator according to aspect 10, wherein the glass support layer is doped to match the thermal expansion coefficient of the glass support layer with the thermal expansion coefficient of the piezoelectric layer.

[0133] Aspect 12. The SAW resonator according to aspect 10, wherein the glass support layer is formed of amorphous SiO2.

[0134] Aspect 13. The SAW resonator according to aspect 10, wherein the glass support layer is formed of crystalline SiO2.

[0135] Aspect 14. The SAW resonator according to any one of Aspects 1 to 13, wherein the piezoelectric layer comprises lithium tantalate (LT) or lithium niobate (LN), wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ) and theta (θ).

[0136] Aspect 15. The SAW resonator according to aspect 14, wherein the µ value is in the range of -80 degrees to -30 degrees.

[0137] Aspect 16. The SAW resonator according to aspect 14, wherein the piezoelectric layer is in a configuration selected from LT0 to LT60.

[0138] Aspect 17. The SAW resonator according to aspect 14, wherein the piezoelectric layer is in a configuration selected from LT25 to LT50.

[0139] Aspect 18. The SAW resonator according to aspect 14, wherein the thickness of the piezoelectric layer is approximately 0.4 times the pitch value of the fingers of the interdigital transducer.

[0140] Aspect 19. The SAW resonator according to aspect 14, wherein the thickness of the piezoelectric layer is between 0.2 and 0.8 times the pitch value of the fingers of the interdigital transducer.

[0141] Aspect 20. The SAW resonator according to any one of Aspects 1 to 19, wherein the thickness of the AlN substrate layer is less than four times the pitch value.

[0142] Aspect 21. The SAW resonator according to any one of Aspects 1 to 20, the SAW resonator further comprising: a SiO2 compensation layer, the SiO2 compensation layer being located between the piezoelectric layer and the AlN substrate layer.

[0143] Aspect 22. The SAW resonator according to aspect 21, wherein the SiO2 compensation layer is approximately between 0.2 and 0.8 times the pitch value of the fingers of the interdigital transducer.

[0144] Aspect 23. The SAW resonator according to any one of Aspects 1 to 13, wherein the piezoelectric layer comprises lithium tantalate, and wherein the Euler angle is selected from the set of lithium tantalate Euler angles including LT15, ​​LT20, LT30, LT36, LT39, LT42, LT46.3 and LT50.

[0145] Aspect 24. The resonator according to any one of Aspects 1 to 23, wherein the piezoelectric layer and the interdigital transducer are configured to excite a specific shear polarization wave mode.

[0146] Aspect 25. A surface acoustic wave (SAW) filter device, the SAW filter device comprising: a substrate layer comprising an aluminum nitride (AlN) substrate layer; an electrode structure comprising an interdigital transducer having an input terminal, an output terminal, and a center track; and a piezoelectric layer disposed between the electrode structure and the substrate layer, wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ), wherein the substrate layer and the piezoelectric layer are configured for the excitation of a selected electroacoustic mode, the excitation of the selected electroacoustic mode being constrained by the AlN substrate layer to limit the excitation of stray modes in the stacked structure of the SAW filter device.

[0147] Aspect 26. The SAW filter device according to aspect 25, wherein the piezoelectric layer comprises lithium tantalate, and wherein the Euler angle for the piezoelectric layer is selected in the range of LT0 to LT60.

[0148] Aspect 27. A surface acoustic wave (SAW) resonator, the SAW resonator comprising: a glass support layer; a substrate layer disposed on the glass support layer, the substrate layer comprising an aluminum nitride (AlN) substrate layer; a fast layer disposed on the AlN substrate layer; an electrode structure comprising an interdigital transducer; and a piezoelectric layer disposed between the electrode structure and the fast layer.

[0149] Aspect 28. The SAW resonator according to aspect 27, wherein the slow layer is a silicon oxide (SiO2) layer.

[0150] Aspect 29. The SAW resonator according to any one of Aspects 27 to 28, the SAW resonator further comprising: a scandium-doped aluminum nitride (AlScN) layer disposed between the substrate layer and the piezoelectric layer.

[0151] Aspect 30. A method comprising: forming a substrate layer comprising an aluminum nitride (AlN) substrate layer; forming a piezoelectric layer on a top surface of the substrate layer, wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ); and forming an electrode layer on the top surface of the piezoelectric layer, wherein the substrate layer and the piezoelectric layer are configured for surface wave excitation, and wherein the AlN substrate layer is configured as a fast layer to confine stray wave excitation.

[0152] Aspect 31. A method of forming any device according to aspects 1 to 29 above.

[0153] Aspect 32. An apparatus comprising components for operating as a SAW resonator according to any one of aspects 1 to 29 above.

Claims

1. A surface acoustic wave (SAW) resonator, the surface acoustic wave (SAW) resonator comprising: The substrate layer includes an aluminum nitride (AlN) substrate layer. Electrode structure, said electrode structure including interdigital transducers, and A piezoelectric layer is disposed between the electrode structure and the substrate layer.

2. The SAW resonator of claim 1, wherein the substrate layer and the piezoelectric layer are configured for surface wave excitation, and wherein the AlN substrate layer is configured as a fast layer to confine wave energy to the top surface of the SAW resonator.

3. The SAW resonator according to claim 1, wherein the piezoelectric layer comprises lithium tantalate (LT) or lithium niobate (LN).

4. The SAW resonator according to claim 1, wherein the AlN substrate layer is a single-crystal AlN layer.

5. The SAW resonator according to claim 1, wherein the AlN substrate layer is a ceramic AlN layer.

6. The SAW resonator according to claim 5, wherein the AlN substrate layer is fabricated as a non-piezoelectric layer using a ceramic material and disordered polycrystalline AlN or amorphous AlN.

7. The SAW resonator according to claim 1, wherein the AlN substrate layer is a deposited thin film layer.

8. The SAW resonator of claim 7, wherein the AlN substrate layer is configured to adjust the speed (v) sh Scandium-doped thin film layer with a value of ) 9. The SAW resonator according to claim 8, wherein the substrate layer further comprises a glass support layer, wherein the AlN substrate layer is disposed between the piezoelectric layer and the glass support layer.

10. The SAW resonator according to claim 1, wherein the substrate layer further comprises a glass support layer, wherein the AlN substrate layer is disposed between the glass support layer and the piezoelectric layer.

11. The SAW resonator of claim 9, wherein the glass support layer is doped to match the coefficient of thermal expansion of the glass support layer with the coefficient of thermal expansion of the piezoelectric layer.

12. The SAW resonator of claim 10, wherein the glass support layer is formed of amorphous SiO2.

13. The SAW resonator of claim 10, wherein the glass support layer is formed of crystalline SiO2.

14. The SAW resonator of claim 1, wherein the piezoelectric layer comprises lithium tantalate (LT), and wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ).

15. The SAW resonator of claim 14, wherein μ is a value in the range of -80 degrees to -30 degrees.

16. The SAW resonator of claim 14, wherein the piezoelectric layer is in a configuration selected from LT0 to LT60.

17. The SAW resonator of claim 14, wherein the piezoelectric layer is in a configuration selected from LT25 to LT50.

18. The SAW resonator of claim 14, wherein the thickness of the piezoelectric layer is approximately 0.4 times the pitch value of the fingers of the interdigital transducer.

19. The SAW resonator of claim 14, wherein the thickness of the piezoelectric layer is between 0.2 and 0.8 times the pitch value of the fingers of the interdigital transducer.

20. The SAW resonator of claim 18, wherein the thickness of the AlN substrate layer is less than four times the pitch value.

21. The SAW resonator according to claim 1, further comprising: A SiO2 compensation layer is located between the piezoelectric layer and the AlN substrate layer.

22. The SAW resonator of claim 21, wherein the SiO2 compensation layer is approximately between 0.2 and 0.8 times the pitch value of the fingers of the interdigital transducer.

23. The SAW resonator of claim 1, wherein the piezoelectric layer comprises lithium tantalate (LT), and wherein the Euler angles for the LT are selected from the set of LT Euler angles including LT15, ​​LT20, LT30, LT36, LT39, LT42, LT46.3 and LT50.

24. The SAW resonator of claim 1, wherein the substrate layer further comprises a glass support layer, wherein the AlN substrate layer is disposed between the glass support layer and the piezoelectric layer; and The glass support layer is doped to match the coefficient of thermal expansion of the glass support layer with that of the piezoelectric layer.

25. A surface acoustic wave (SAW) filter device, the surface acoustic wave (SAW) filter device comprising: The substrate layer includes an aluminum nitride (AlN) substrate layer. The electrode structure includes an interdigital transducer having an input terminal, an output terminal, and a central track. A piezoelectric layer is disposed between the electrode structure and the substrate layer, wherein the crystal structure of the piezoelectric layer is defined by Euler angles lambda (λ), mu (µ), and theta (θ), wherein the substrate layer and the piezoelectric layer are configured for the excitation of a selected electroacoustic mode, the excitation of which is constrained by the AlN substrate layer to limit the excitation of stray modes in the stacked structure of the SAW filter device.

26. The SAW filter device of claim 25, wherein the piezoelectric layer comprises lithium tantalate, and wherein the Euler angle for the piezoelectric layer is selected in the range of LT0 to LT60.

27. A surface acoustic wave (SAW) resonator, the surface acoustic wave (SAW) resonator comprising: Glass support layer, A substrate layer is disposed on the glass support layer, and the substrate layer includes an aluminum nitride (AlN) substrate layer. The slow layer is disposed on the AlN substrate layer. Electrode structure, said electrode structure including interdigital transducers, and A piezoelectric layer is disposed between the electrode structure and the slow layer.

28. The SAW resonator of claim 27, wherein the slow layer is a silicon oxide (SiO2) layer.

29. The SAW resonator of claim 27, further comprising: A scandium-doped aluminum nitride (AlScN) layer is disposed between the substrate layer and the piezoelectric layer.

30. A method comprising: A substrate layer comprising an aluminum nitride (AlN) substrate layer is formed. A piezoelectric layer is formed on the top surface of a substrate layer, wherein the crystalline structure of the piezoelectric layer is defined by Euler angles lambda(λ), mu(µ), and theta(θ), and An electrode layer is formed on the top surface of the piezoelectric layer, wherein the substrate layer and the piezoelectric layer are configured for surface wave excitation, and wherein the AlN substrate layer is configured as a fast layer to limit stray wave excitation.

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