Partial suspension of piezoelectric layer using dielectric

Abstract

An apparatus for partially suspending a piezoelectric layer using a dielectric is disclosed. In an example aspect, the device includes a microacoustic filter having a substrate layer (126), a piezoelectric layer (128), an electrode structure (310) in contact with the piezoelectric layer, and a dielectric (130). The electrode structure includes a plurality of fingers arranged across a plane having a first axis (406) perpendicular to the plurality of fingers and a second axis (408) parallel to the plurality of fingers. The dielectric is configured to separate the piezoelectric layer from the base layer and define a cavity (316) between the piezoelectric layer and the base layer. The dielectric is also configured to support the piezoelectric layer across at least three points (314) along the first axis.

Description

Technical Field

[0001] The present disclosure relates generally to wireless transceivers and other components employing filters, and more particularly to microacoustic filters having a dielectric that partially suspends a piezoelectric layer from a base layer. Background Art

[0002] Electronic devices use radio frequency (RF) signals to communicate information. These RF signals enable users to talk with friends, download information, share pictures, remotely control home devices, and receive global positioning information. In order to send or receive RF signals within a given frequency band, electronic devices may use filters to pass signals within the band and suppress (e.g., attenuate) interference or noise with frequencies outside the band. However, designing filters that provide filtering for RF applications, including those utilizing frequencies above 2 gigahertz (GHz), can be challenging. Summary of the invention

[0003] A device implementing a technique for partially suspending a piezoelectric layer using a dielectric is disclosed. In an example implementation, a microacoustic filter includes a substrate layer, a piezoelectric layer, and a dielectric. The dielectric at least partially covers the piezoelectric layer and partially suspends the piezoelectric layer "above" or separates it from the substrate layer. Due to the partial covering and partial suspension, a cavity exists between the dielectric and the substrate layer.

[0004] By using a partially suspended piezoelectric layer, the microacoustic filter can excite and limit the plate mode, and relative to other microacoustic filters that excite surface acoustic wave modes, the microacoustic filter has a larger spacing at frequencies above, for example, 2 GHz. This larger spacing can make it easier to manufacture the electrode structure of the microacoustic filter. In addition, relative to other acoustic filters with a fully suspended piezoelectric layer, the microacoustic filter can have improved mechanical stability, improved thermal management, and a smaller absolute value of the frequency temperature coefficient.

[0005] In an example aspect, a device for filtering is disclosed. The device includes a microacoustic filter having a substrate layer, a piezoelectric layer, an electrode structure in contact with the piezoelectric layer, and a dielectric. The electrode structure includes a plurality of fingers arranged across a plane having a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers. The dielectric is configured to separate the piezoelectric layer from the substrate layer and define a cavity between the piezoelectric layer and the substrate layer. The dielectric is also configured to support the piezoelectric layer across at least three points along the first axis.

[0006] In an example aspect, a device for filtering is disclosed. The device includes a microacoustic filter configured to generate a filter signal from a radio frequency signal. The microacoustic filter includes a component for converting the radio frequency signal into an acoustic wave and converting the formed acoustic wave into the filter signal. The microacoustic filter also includes a component for exciting an antisymmetric plate mode. The microacoustic filter additionally includes a component for confining the energy of the antisymmetric plate mode within the component for exciting. The microacoustic filter further includes a component for partially suspending the component for exciting and separating it from the component for limiting energy.

[0007] In an example aspect, a method for manufacturing a microacoustic filter is disclosed. The method includes providing a substrate layer and providing a piezoelectric layer. The method also includes providing an electrode structure having a plurality of fingers arranged across a plane. The plane is defined by a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers. The electrode structure is in contact with the piezoelectric layer. The method additionally includes providing a dielectric that separates the piezoelectric layer from the substrate layer, defines a cavity between the piezoelectric layer and the substrate layer, and supports the piezoelectric layer across at least three points along the first axis.

[0008] In an example aspect, a microacoustic filter is disclosed. The microacoustic filter includes an electrode structure, a substrate layer, a piezoelectric layer, and a dielectric. The electrode structure includes a plurality of fingers arranged across a plane having a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers. The piezoelectric layer has a surface facing the substrate layer. The dielectric includes an intermediate layer and at least three columns. The intermediate layer is arranged across the surface of the piezoelectric layer. The intermediate layer has a surface facing the substrate layer. The at least three columns extend through a plane defined by the surface of the intermediate layer and extend toward the substrate layer to define a cavity between the intermediate layer and the substrate layer. The at least three columns are positioned across at least three points along the first axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An example operating environment for partially suspending a piezoelectric layer using a dielectric is illustrated.

[0010] Figure 2 An example wireless transceiver including at least one microacoustic filter having a dielectric that partially suspends a piezoelectric layer is illustrated.

[0011] Figure 3-1 An example assembly of a microacoustic filter having a dielectric that partially suspends a piezoelectric layer is illustrated.

[0012] Figure 3-2 Example Euler angles defining the orientation of the piezoelectric material of a microacoustic filter are illustrated.

[0013] Figure 4 A first example implementation of a microacoustic filter having a dielectric that partially suspends a piezoelectric layer is illustrated.

[0014] Figure 5 Examples of intermediate layers of dielectric and posts that partially suspend the piezoelectric layer are illustrated.

[0015] Figure 6 A second example implementation of a microacoustic filter having a dielectric that partially suspends a piezoelectric layer is illustrated.

[0016] Figure 7 A third example implementation of a microacoustic filter having a dielectric that partially suspends a piezoelectric layer is illustrated.

[0017] Figure 8 A fourth example implementation of a microacoustic filter having a dielectric that partially suspends a piezoelectric layer is illustrated.

[0018] Fig. 9 is a flow chart illustrating an example process for fabricating a microacoustic filter having a dielectric that partially suspends a piezoelectric layer. DETAILED DESCRIPTION

[0019] To send or receive radio frequency signals within a given frequency band, electronic devices may use filters to pass signals within the frequency band and suppress (e.g., attenuate) interference or noise with frequencies outside the frequency band. Electroacoustic devices (e.g., "acoustic filters") may be used to filter high-frequency signals (such as those with frequencies greater than 100 megahertz (MHz)) in many applications. Acoustic filters are tuned to pass certain frequencies (e.g., frequencies within their passband) and attenuate other frequencies (e.g., frequencies outside their passband). Using piezoelectric materials, acoustic filters operate by transforming an electrical signal wave applied to an electrical conductor into an acoustic wave (e.g., an acoustic signal wave) formed across the piezoelectric material. The acoustic wave is then converted back into an electrical filter signal. Acoustic filters may include electrode structures that transform or convert between electromagnetic waves and acoustic waves.

[0020] Acoustic waves are characterized by a velocity that has a magnitude much smaller than the velocity of electromagnetic waves. Generally speaking, the magnitude of the propagation velocity of a wave is proportional to the size of the wavelength of the wave. Therefore, after converting the electrical signal wave into an acoustic signal wave, 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 wave enables 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.

[0021] However, it can be challenging to design acoustic filters that can provide filtering for higher frequencies, such as those used in bands 7, 40, n77, and n79; 5 GHz frequency; frequencies below 6 GHz, and / or frequencies between 6 GHz and 13 GHz. Specifically, due to lithographic constraints, the spacing of the electrode structures may become too small for manufacturing equipment or may be less practical or too costly to produce accurately. The spacing may also introduce issues involving electrostatic discharge or power durability.

[0022] To address this challenge, some technologies implement acoustic filters with a piezoelectric layer that is fully suspended and excites and confines plate modes. In order to fully suspend the piezoelectric layer, the acoustic filter has supports positioned at two opposite edges of the piezoelectric layer along the direction of acoustic wave propagation. However, with only two supports at the outer edges of the piezoelectric layer, this design may be mechanically unstable.

[0023] The complete suspension of the piezoelectric layer may also result in a larger absolute value of the temperature coefficient of frequency (TCF) compared to other acoustic filters with non-suspended piezoelectric layers. The temperature coefficient of frequency characterizes the amount by which the resonant frequency or the skirt of the filter changes in response to temperature changes. A filter with a smaller absolute value of the temperature coefficient of frequency has a more stable frequency response over a certain temperature range compared to another filter with a larger absolute value of the temperature coefficient of frequency.

[0024] In order to provide specific performance improvements, a technique for partially suspending a piezoelectric layer using a dielectric is described. In an example implementation, a microacoustic filter includes a substrate layer, an electrode structure, a piezoelectric layer, and a dielectric. The dielectric at least partially covers or abuts the piezoelectric layer, and partially suspends the piezoelectric layer "above" or separates it from the substrate layer. Due to the partial coverage and partial suspension, a cavity exists between the dielectric and the substrate layer. Relative to another acoustic filter having a fully suspended piezoelectric layer, the partial coverage enables the microacoustic filter to have a smaller absolute value of the frequency temperature coefficient.

[0025] Compared to a fully suspended piezoelectric layer, a partially suspended piezoelectric layer is supported by a dielectric across three or more points along an axis orthogonal to the longitudinal axis of the fingers of the electrode structure. The additional support points provide the microacoustic filter with improved mechanical stability, thermal management, and power dissipation relative to another acoustic filter having a fully suspended piezoelectric layer. In some cases, one or more dielectric supports may be positioned "under" a portion of the electrode structure of the microacoustic filter (e.g., between the fingers of the electrode structure and the substrate layer).

[0026] By using the technology of partially suspending the piezoelectric layer with a dielectric, the microacoustic filter can excite and limit the plate mode. Compared with another microacoustic filter that excites a surface acoustic wave mode (such as a Rayleigh mode or a shear mode), the plate mode enables the microacoustic filter to have a larger spacing at a frequency above 2 GHz, for example. This larger spacing can make it easier to manufacture the electrode structure of the microacoustic filter. In addition, by partially suspending the piezoelectric layer, the microacoustic filter can have improved mechanical stability, improved thermal management, and a smaller absolute value of the frequency temperature coefficient relative to another acoustic filter with a fully suspended piezoelectric layer. These techniques can be used with microacoustic filters that support frequencies above 2 GHz and other microacoustic filters that support frequencies below 2 GHz and provide beneficial effects for them.

[0027] Figure 1 An example environment 100 for partially suspending a piezoelectric layer using a dielectric is illustrated. In the 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 smart phone. However, the computing device 102 can be implemented as any suitable computing or electronic device, such as a modem, a cellular base station, a broadband router, an access point, a cellular phone, a gaming device, a navigation device, a media device, a laptop computer, a desktop computer, a tablet computer, a wearable computer, a server, a network attached storage (NAS) device, a smart appliance or other Internet of Things (IoT) device, a medical device, a vehicle-based communication system, a radar, a radio, and the like.

[0028] Base station 104 communicates with computing device 102 via wireless link 106, which may be implemented as any suitable type of wireless link. Although depicted as a cellular network tower, base station 104 may represent or be implemented as another device, such as a satellite, a server device, a terrestrial television broadcast tower, an access point, a peer device, a mesh network node, etc. Thus, computing device 102 may communicate with base station 104 or another device via a wireless connection.

[0029] Wireless link 106 may include a downlink of data or control information communicated from base station 104 to computing device 102, an uplink of other data or control information communicated from computing device 102 to base station 104, or both. Wireless link 106 may be implemented using any suitable communication protocol or standard, such as second generation (2G), third generation (3G), fourth generation (4G), or fifth generation (5G) cellular; IEEE 802.11 (e.g., ); IEEE 802.15 (e.g., ); IEEE 802.16 (e.g., ); etc. In some implementations, the wireless link 106 can provide power wirelessly, and the base station 104 or the computing device 102 can include a power source.

[0030] As shown, computing device 102 includes an application processor 108 and a computer-readable storage medium 110 (CRM 110). Application processor 108 may include any type of processor, such as a multi-core processor, that executes processor executable code stored by CRM 110. 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 the present disclosure, CRM 110 is implemented to store instructions 112, data 114, and other information for computing device 102, and therefore does not include transient propagating signals or carrier waves.

[0031] The computing device 102 may also include input / output ports 116 (I / O ports 116) and a display 118. The I / O ports 116 enable data exchange or interaction with other devices, networks, or users. The I / O ports 116 may include serial ports (e.g., universal serial bus (USB) ports), parallel ports, audio ports, infrared (IR) ports, user interface ports such as a touch screen, and the like. The display 118 presents graphics of 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 a virtual interface through which the graphical content of the computing device 102 is presented.

[0032] The wireless transceiver 120 of the computing device 102 provides connectivity to a corresponding network and other electronic devices connected thereto. The wireless transceiver 120 may facilitate communication over any suitable type of wireless network, such as a wireless local area network (WLAN), a peer-to-peer (P2P) network, a mesh network, a cellular network, an ultra-wideband (UWB) network, a wireless wide area network (WWAN), and / or a wireless personal area network (WPAN). In the context of the example environment 100, the wireless transceiver 120 enables the computing device 102 to communicate with the base station 104 and the network connected thereto. However, the wireless transceiver 120 may also enable the computing device 102 to communicate "directly" with other devices or networks.

[0033] The wireless transceiver 120 includes circuits and logic for sending and receiving communication signals via the antenna 122. The components of the 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). The 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, the components of the wireless transceiver 120 are implemented as separate transmitter and receiver entities. Additionally or alternatively, the wireless transceiver 120 may be implemented using multiple or different parts to implement corresponding transmission and reception operations (e.g., separate transmission chains and reception chains). In general, the wireless transceiver 120 processes data and / or signals associated with data communicated to the computing device 102 via the antenna 122.

[0034] exist Figure 1 In the example shown, the wireless transceiver 120 includes at least one microacoustic filter 124 (e.g., an acoustic filter, a plate mode acoustic wave filter, or a membrane filter). In some specific implementations, the wireless transceiver 120 includes a plurality of microacoustic filters 124, which may be formed by microacoustic resonators arranged in series, in parallel, in a ladder structure, in a grid structure, or in some combination thereof. Although the microacoustic filter 124 may be any type of microacoustic filter, the technique of partially suspending the piezoelectric layer using a dielectric may be particularly advantageous for confining plate mode acoustic waves within the piezoelectric layer 128. One such example acoustic mode is a plate mode, such as an antisymmetric plate mode (e.g., an antisymmetric Lamb mode). The antisymmetric plate mode may be a first order (e.g., A1) mode or a higher order mode (e.g., A3). The antisymmetric plate mode excitation causes different portions (e.g., an upper portion and a lower portion) of the piezoelectric layer 128 to move in opposite directions along the horizontal dimension. The antisymmetric plate mode is a quasi-steady-state mode with a group velocity of approximately zero.

[0035] The microacoustic filter 124 includes at least one substrate layer 126, at least one piezoelectric layer 128, a dielectric 130 (e.g., a dielectric material or at least one dielectric layer), and at least one metal layer 132. The dielectric 130 at least partially implements the technology of partially suspending the piezoelectric layer 128. Specifically, the dielectric 130 partially covers the piezoelectric layer 128 and partially suspends the piezoelectric layer 128 "above" or separates it from the substrate layer 126. The dielectric 130 also defines or forms a cavity between the partially covered piezoelectric layer 128 and the substrate layer 126. The cavity enables the piezoelectric layer 128 to excite the plate mode and confine the sound waves within the piezoelectric layer 128, which reduces the acoustic loss. The metal layer 132 includes an electrode structure (e.g., Figure 3-1 The electrode structure 302 may be partially disposed within the dielectric 130, partially disposed within the piezoelectric layer 128, or both.

[0036] Utilizing techniques for partially suspending the piezoelectric layer 128, the microacoustic filter 124 can have fewer lithographic constraints at higher frequencies than other microacoustic filters that excite surface acoustic wave modes. Thus, the microacoustic filter 124 can be designed to support a frequency range above 2 GHz, including frequencies between approximately 4 GHz and 13 GHz (e.g., approximately 4 GHz, 7 GHz, 10 GHz, or 13 GHz). Generally speaking, the term "approximately" can mean that any frequency can be within + / - 10% or less of a specified value (e.g., within + / - 5%, + / - 3%, or + / - 2% of a specified value). With regard to Figure 2 The microacoustic filter 124 is further described.

[0037] 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 implementations, the transmitter 202 and the receiver 204 can be connected to the same antenna through a duplexer (not shown). The transmitter 202 is shown to include 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 micro-acoustic filter 124-1. The receiver 204 includes at least one second micro-acoustic filter 124-2, at least one amplifier 212 (e.g., a low noise amplifier), at least one second mixer 208-2, and at least one analog-to-digital converter 214 (ADC 214). The first mixer 208-1 and the second mixer 208-2 are coupled to a local oscillator 216. Although not explicitly shown, the digital-to-analog converter 206 of the transmitter 202 and the analog-to-digital converter 214 of the receiver 204 may be coupled to ( Figure 1 ) application processor 108 or another processor associated with the wireless transceiver 120 (e.g., a modem).

[0038] In some implementations, wireless transceiver 120 is implemented using multiple circuits (e.g., multiple integrated circuits) such as transceiver circuit 236 and radio frequency front end (RFFE) circuit 238. Thus, the components that form transmitter 202 and receiver 204 are distributed across these circuits. Figure 2As shown, the transceiver circuit 236 includes the digital-to-analog converter 206 of the transmitter 202, the mixer 208-1 of the transmitter 202, the mixer 208-2 of the receiver 204, and the analog-to-digital converter 214 of the receiver 204. In other specific implementations, the digital-to-analog converter 206 and the analog-to-digital converter 214 can be implemented on another separate circuit including the application processor 108 or the modem. The RF front-end circuit 238 includes the amplifier 210 of the transmitter 202, the micro-acoustic filter 124-1 of the transmitter 202, the micro-acoustic filter 124-2 of the receiver 204, and the amplifier 212 of the receiver 204.

[0039] During transmission, the transmitter 202 generates a radio frequency transmit signal 218 that is transmitted using the antenna 122-1. To generate the radio frequency transmit signal 218, the digital-to-analog converter 206 provides a pre-up-converted transmit signal 220 to the first mixer 208-1. The pre-up-converted transmit signal 220 may be a baseband signal or an intermediate frequency signal. The first mixer 208-1 uses a local oscillator (LO) signal 222 provided by the local oscillator 216 to up-convert the pre-up-converted transmit signal 220. The first mixer 208-1 generates an up-converted signal, which is referred to as a pre-filter transmit signal 224. The pre-filter transmit signal 224 may be a radio frequency signal and include some noise or unwanted frequencies, such as harmonic frequencies. The amplifier 210 amplifies the pre-filter transmit signal 224 and passes the amplified pre-filter transmit signal 224 to the first micro-acoustic filter 124-1.

[0040] The first micro-acoustic filter 124-1 filters the amplified pre-filter transmit signal 224 to generate a filtered transmit signal 226. As part of the filtering process, the first micro-acoustic filter 124-1 attenuates noise or unwanted frequencies within the pre-filter 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.

[0041] During reception, antenna 122-2 receives RF receive signal 228 and passes RF receive signal 228 to receiver 204. Second micro-acoustic filter 124-2 accepts received RF receive signal 228, which is represented by pre-filter receive signal 230. Second micro-acoustic filter 124-2 filters any noise or unwanted frequencies within pre-filter receive signal 230 to generate filtered receive signal 232.

[0042] The amplifier 212 of the receiver 204 amplifies the filtered received signal 232 and passes the amplified filtered received signal 232 to the second mixer 208-2. The second mixer 208-2 downconverts the amplified filtered received signal 232 using the local oscillator signal 222 to generate a downconverted received signal 234. The analog-to-digital converter 214 converts the downconverted received signal 234 into a digital signal that can be processed by the application processor 108 or another processor associated with the wireless transceiver 120 (e.g., a modem).

[0043] Figure 2 1 illustrates one example configuration of the wireless transceiver 120. Other configurations of the wireless transceiver 120 may support multiple frequency bands and share the antenna 122 across multiple transceivers. A person of ordinary skill in the art may appreciate various other configurations that may include the micro-acoustic filter 124. For example, the micro-acoustic filter 124 may be integrated into a duplexer or a diplexer of the wireless transceiver 120. Figure 8 An example implementation of the microacoustic filter 124 - 1 or 124 - 2 is further described.

[0044] Figure 3-1 Example components of a microacoustic filter 124 are illustrated. In the depicted configuration, the microacoustic filter 124 includes an electrode structure 302, a dielectric 130 (e.g., a dielectric material), a piezoelectric layer 128, and a substrate layer 126. The electrode structure 302 includes 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 adhesion layers. As an example, the metal layer may be composed of aluminum (Al), copper (Cu), silver (Ag), gold (Au), tungsten (W), or some combination or doping thereof. The adhesion layer may be composed of chromium (Cr), titanium (Ti), molybdenum (Mo), or some combination thereof.

[0045] The electrode structure 302 may include one or more interdigital transducers 304. The interdigital transducers 304 convert electrical signals into acoustic waves and convert acoustic waves into filtered electrical signals. The interdigital transducers 304 include at least two comb structures 306-1 and 306-2. Each comb structure 306-1 and 306-2 includes a busbar 308 (e.g., a conductive segment or conductive rail) and a plurality of fingers 310 (e.g., electrode fingers). Figure 4 An example interdigital transducer 304 is further described. Although not explicitly shown, the electrode structure 302 may also include two or more reflectors. In an example implementation, the interdigital transducer 304 is disposed between two reflectors.

[0046] The dielectric 130 includes at least one intermediate layer 312 and at least three pillars 314. The intermediate layer 312 refers to a portion of the dielectric 130 that may be disposed on the piezoelectric layer 128. Generally, the intermediate layer 312 adheres to the piezoelectric layer 128 and serves as a base or frame for partially suspending the piezoelectric layer 128.

[0047] The thickness of the intermediate layer 312 can be designed to achieve a specific frequency temperature coefficient. Generally speaking, increasing the thickness of the intermediate layer 312 will reduce the absolute value of the frequency temperature coefficient. However, the thickness of the intermediate layer 312 can be limited to prevent spurious modes from negatively affecting performance.

[0048] The pillars 314 are disposed between the intermediate layer 312 and the base layer 126. The pillars 314 provide structural support to elevate the intermediate layer 312 above the base layer 126. By elevating the intermediate layer 312, the pillars 314 suspend at least a portion of the piezoelectric layer 128 away from the base layer 126. The pillars 314 are positioned at different points along an axis orthogonal to the longitudinal axis of the fingers 310 of the electrode structure 302. In this way, the pillars 314 improve the mechanical stability of the microacoustic filter 124 compared to other acoustic filters having a fully suspended piezoelectric layer.

[0049] The columns 314 define a cavity 316 (or gap) between the intermediate layer 312 and the base layer 126. The cavity 316 may include a gas, such as air. The columns 314 provide stability and support to prevent the cavity 316 from collapsing. In some implementations, at least one of the columns 314 is positioned "under" one of the fingers 310. Sometimes, the number of columns 314 is equal to the number of fingers 310. In this case, each column 314 may be positioned "under" a corresponding finger 310. Generally speaking, it may be advantageous to position the columns 314 under a portion of the electrode structure 302 because the acoustic waves (or plate waves) are spatially confined between the fingers 310 of the electrode structure 302. Therefore, this positioning may reduce the effect of the columns 314 on the acoustic waves.

[0050] The dielectric 130 may be formed using a variety of different types of dielectric materials, such as silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3), aluminum nitride (AlN), or some combination or doped form thereof. The doped form of silicon dioxide may include fluoride-doped silicon dioxide (e.g., silicon oxyfluoride (SiO2F)) or carbon-doped silicon dioxide (e.g., oxidized silicon carbide (SiO2C)). In some implementations, the dielectric 130 is composed of multiple layers. The multiple layers may be formed using the same material or different materials. In addition, the intermediate layer 312 and the pillars 314 may be implemented using the same material or different materials. In an example implementation, the total thickness of the dielectric 130 (e.g., the combined thickness of the intermediate layer 312 and the pillars 314) may be between about 50 nanometers and 1 micron. In general, the term "about" may mean that any thickness may be within + / -10% or less of a specified value (e.g., within + / -5%, + / -3%, or + / -2% of a specified value).

[0051] In some implementations, the microacoustic filter 124 includes additional dielectric layers, such as Figure 8 The dielectric layer shown in FIG. 1 also enables the target temperature coefficient of frequency to be achieved.

[0052] In an example implementation, the piezoelectric layer 128 may be implemented using a variety of different materials that exhibit piezoelectric properties (e.g., can convert mechanical energy into electrical energy or convert electrical energy into mechanical energy). Example types of materials include lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, aluminum nitride (AlN), aluminum scandium nitride (AlScN), or some combination thereof. Generally speaking, the material forming the piezoelectric layer 128 has a crystal structure. This crystal structure is defined by an ordered arrangement of particles (e.g., atoms, ions, or molecules). The crystal structure of the piezoelectric layer 128 can be defined by the Euler angles lambda (λ), mu (μ), and theta (θ).

[0053] In some aspects, the material and crystal structure of the piezoelectric layer 128 are selected such that the piezoelectric layer 128 excites an antisymmetric plate mode. Consider two examples of using lithium niobate to form the piezoelectric layer 128. In a first example implementation, the lithium niobate material is cut such that the value of the Euler angle mu (μ) is about 38°, and the values ​​of the Euler angles lambda (λ) and theta (θ) are about 0° (or at least one symmetrical equivalent thereof). In a second example implementation, the lithium niobate material is cut such that the value of the Euler angle theta (θ) is about 90°, and the values ​​of the Euler angles lambda (λ) and mu (μ) are about zero (or at least one symmetrical equivalent thereof). In general, the term "about" may mean that any angle may be within + / -10% or less of the specified value (e.g., within + / -5%, + / -3%, or + / -2% of the specified value).

[0054] In another example, lithium tantalate is used to form the piezoelectric layer 128. In this case, the lithium tantalate material is cut so that the value of the Euler angle mu (μ) is about 42°, and the values ​​of the Euler angles lambda (λ) and theta (θ) are about 0° (or at least one symmetrical equivalent thereof). In general, the term "about" can mean that any angle can be within + / -10% or less of the specified value (e.g., within + / -5%, + / -3%, or + / -2% of the specified value). With respect to Figure 3-2 Euler angles are described further.

[0055] The base layer 126 includes one or more sub-layers that can support passivation, temperature regulation, power handling, mode suppression, etc. As an example, the base layer 126 can include at least one charge trapping layer 318 (e.g., at least one trapping enriched layer), at least one support layer 320, or some combination thereof. These sub-layers can be considered part of the base layer 126 or their own separate layers. In one example implementation, the base layer 126 includes a single support layer 320 formed using a silicon (Si) material.

[0056] The charge trapping layer 318 can trap induced charges at the interface between the compensation layer and the support layer, for example, to suppress nonlinear substrate effects. The charge trapping layer 318 can include at least one polycrystalline silicon (poly-Si) layer (e.g., a polycrystalline silicon layer or a multicrystalline silicon layer), at least one amorphous silicon layer, at least one silicon nitride (SiN) layer, at least one silicon oxynitride (SiON) layer, at least one aluminum nitride (AlN) layer, diamond-like carbon (DLC), diamond, or some combination thereof.

[0057] The support layer 320 can reduce the amount of energy leaking into the base layer 126. In some implementations, the support layer 320 can also serve as the compensation layer 318. Generally speaking, the support layer 320 is composed of a material that is non-conductive and provides isolation. For example, the support layer 320 can be formed using a silicon (Si) material (e.g., a doped high-resistance silicon material), a sapphire material (e.g., aluminum oxide (Al2O3)), a silicon carbide (SiC) material, a fused silica material, quartz, glass, diamond, or some combination thereof. In some implementations, the support layer 320 has a relatively similar thermal expansion coefficient (TEC) to the piezoelectric layer 128. The support layer 320 can also have a specific crystal orientation to support the suppression or attenuation of stray modes.

[0058] In some aspects, the microacoustic filter 124 can be considered a resonator. Sometimes, the microacoustic filter 124 can be connected to other resonators associated with a layer stack different from the microacoustic filter 124. In other aspects, the microacoustic filter 124 can be implemented as multiple interconnected resonators using the same layers (e.g., substrate layer 126, piezoelectric layer 128, and / or dielectric 130).

[0059] Figure 3-2 Example Euler angles that define the orientation of a piezoelectric layer 128 relative to a crystal structure of a material forming the piezoelectric layer 128 are illustrated. In this example, the material forming the piezoelectric layer 128 includes lithium niobate. A first crystal (X') axis 326, a second crystal (Y') axis 328, and a third crystal (Z') axis 330 are fixed along crystal axes of the lithium niobate crystal. A first rotation 324-1 is applied to rotate the first crystal X' axis 326 and the second crystal Y' axis 328 about the third crystal Z' axis 330. Specifically, the first rotation 324-1 rotates the first crystal X' axis 326 in the direction of the second crystal Y' axis 328. The angle associated with the first rotation 324-1 represents one of the Euler angles, which is represented by the Euler angle lambda (λ) 332. The resulting rotation axes are represented by a new set of axes: an X" axis 334, a Y" axis 336, and a Z" axis 338. As shown in FIG. Figure 3-2 As shown, the third crystal Z′ axis 330 remains unchanged by the first rotation 324 - 1 , such that the third crystal Z′ axis 330 is equal to the Z″ axis 338 .

[0060] In the second rotation 324-2, the Y" axis 336 and the Z" axis 338 are rotated around the X" axis 334 by another Euler angle, which is represented by the Euler angle mu (μ) 340. In this case, the Y" axis 336 is rotated in the direction of the Z" axis 338. The resulting rotation axes are represented by a new set of axes: X"' axis 342, Y"' axis 344, and Z"' axis 346. Figure 3-2 As shown, the X” axis 334 remains unchanged by the second rotation 324 - 2 , such that the X” axis 334 is equal to the X”′ axis 342 .

[0061] In the third rotation 324-3, the X'" axis 342 and the Y'" axis 344 are rotated about the Z'" axis 346 by an additional Euler angle represented by the Euler angle theta (θ) 348. In this case, the X'" axis 342 is rotated in the direction of the Y'" axis 344. The resulting rotation axes are represented by the first filter (X) axis 350, the second filter (Y) axis 352, and the third filter (Z) axis 354, which correspond to Figure 4 The first (X) axis 406, the second (Y) axis 408 and the third (Z) axis 412. Figure 3-2As shown, the Z' axis 346 remains unchanged by the third rotation 324-3, so that the Z' axis 346 is equal to the third filter Z axis 354. Figure 4 The microacoustic filter 124 is further described.

[0062] Figure 4 A first example implementation of a microacoustic filter 124 is illustrated in which a dielectric 130 partially suspends a piezoelectric layer 128 from a base layer 126. Figure 4 A three-dimensional perspective view 400-1 of the micro-acoustic filter 124 is shown at the top of Figure 4 The bottom of FIG. 4 shows a two-dimensional cross-sectional view 400 - 2 of the microacoustic filter 124 . The microacoustic filter 124 includes a piezoelectric layer 128 , an electrode structure 302 , a dielectric 130 , and a substrate layer 126 . The electrode structure 302 may include one or more interdigital transducers 304 .

[0063] In the depicted configuration shown in the two-dimensional cross-sectional view 400 - 2 , the dielectric 130 covers (eg, is in physical contact with or at least proximate to) a surface 402 - 1 of the piezoelectric layer 128 that faces the substrate layer 126 . Figure 5 The intermediate layer 312 and the pillars 314 of the dielectric 130 are further described.

[0064] Dielectric 130 defines a cavity 316 between piezoelectric layer 128 and base layer 126. In some cases, cavity 316 can be considered a collection of multiple cavities that do not intersect. In other cases, cavity 316 can be considered a single cavity with intersecting branches. Sometimes, the width of cavity 316 can be approximately equal to the width of the gap that exists between adjacent fingers 310 of electrode structure 302. Generally speaking, the term "approximately" can mean that any width can be within + / -10% or less of a specified value (e.g., within + / -5%, + / -3%, or + / -2% of a specified value). In other embodiments, the width of cavity 316 can be greater than the width of the gap between adjacent fingers 310, such as with respect to Figure 5 as further described.

[0065] In the three-dimensional perspective view 400-1, the IDT 304 is shown as having two comb structures 306-1 and 306-2, wherein the fingers 310 extend toward each other from the two busbars 308. The fingers 310 are arranged in an interlocking manner between the two busbars 308 of the IDT 304 (e.g., arranged in an interdigitated manner). In other words, the fingers 310 connected to the first busbar 308 extend toward the second busbar 308, but are not connected to the second busbar 308. Similarly, the fingers 310 connected to the second busbar 308 extend toward the first busbar 308, but are not connected to the first busbar 308.

[0066] In a direction along the busbar 308, there is an overlap region that includes a central region where a portion of one finger 310 overlaps a portion of an adjacent finger 310. This central region including the overlap may be referred to as an orifice, track, or active region, where an electric field is generated between the fingers 310 to cause an acoustic wave 412 to form in at least this region of the piezoelectric layer 128.

[0067] The physical periodicity of the fingers 310 is referred to as the spacing 404 of the interdigital transducer 304. The spacing 404 can be indicated in various ways. For example, in some aspects, the spacing 404 can correspond to the magnitude of the distance between adjacent fingers 310 of the interdigital transducer 304 in the central region. For example, the distance can be defined as the distance between the center points of each finger in the fingers 310. When the fingers 310 have a uniform width, the distance can usually be measured between the right (or left) edge of one finger 310 and the right (or left) edge of the adjacent finger 310. In some aspects, the average value of the distance between adjacent fingers 310 of the interdigital transducer 304 can be used for the spacing 404. The frequency is at least partially determined by the characteristics of the micro-acoustic filter 124.

[0068] In the three-dimensional perspective view 400-1, the micro-acoustic filter 124 is defined by a first (X) axis 406, a second (Y) axis 408, and a third (Z) axis 410. The first axis 406 and the second axis 408 are parallel to the planar surface of the piezoelectric layer 128, and the second axis 408 is perpendicular to the first axis 406. The third axis 410 is orthogonal (e.g., perpendicular) to the planar surface of the piezoelectric layer 128. The busbars 308 of the interdigital transducer 304 are oriented parallel to the first axis 406. The fingers 310 of the interdigital transducer 304 are oriented parallel to the second axis 408. The fingers 310 generate an electric field in a direction substantially parallel to the first axis 406. The electric field can generate a quasi-steady-state acoustic wave 412, which is spatially trapped within the piezoelectric layer 128 and exists between adjacent fingers 310 of the electrode structure 302.

[0069] Although in Figure 4 Although not shown in the drawings, some examples of the microacoustic filter 124 may place the electrode structure 302 on the second surface 402-2 of the piezoelectric layer 128 facing away from the base layer 126. In other words, the piezoelectric layer 128 may be disposed between the electrode structure 302 and the dielectric 130. Although this may make it easier to manufacture the microacoustic filter 124, the location of the electrode structure 302 on the second surface 402-2 of the piezoelectric layer prevents further adjustment of the frequency response of the microacoustic filter 124 by trimming the piezoelectric layer 128 (e.g., by reducing the thickness of the piezoelectric layer 128).

[0070] Alternatively, other examples of the micro-acoustic filter 124 place the electrode structure 302 between the piezoelectric layer 128 and the dielectric 130, such as Figure 4 In this case, the electrode structure 302 is positioned so that it contacts the first surface 402-1 of the piezoelectric layer 128 that faces the substrate layer 126. This enables the second surface 402-2 of the piezoelectric layer 128 to be trimmed after manufacturing the electrode structure 302. By trimming the piezoelectric layer 128, the frequency response of the microacoustic filter 124 can be tuned.

[0071] There are various ways in which the electrode structure 302 can be positioned between the piezoelectric layer 128 and the dielectric 130. In a first example implementation, the electrode structure 302 is embedded within the dielectric 130 and in contact with the piezoelectric layer 128, as described with respect to FIG. Figure 5 In a second example implementation, the electrode structure 302 is partially embedded in the piezoelectric layer 128 and partially embedded in the piezoelectric layer 128, as described with respect to Figure 6 In a third example implementation, the electrode structure 302 is embedded in the piezoelectric layer 128 and in contact with the dielectric 130, as described with respect to Figure 7 as further described.

[0072] During operation, the microacoustic filter 124 receives RF signals such as Figure 2 , or the pre-filter transmit signal 224 or the pre-filter receive signal 230 shown in . The electrode structure 302 uses the inverse piezoelectric effect to excite the acoustic wave 412 within the piezoelectric layer 128. For example, the interdigital transducers 304 in the electrode structure 302 generate an alternating electric field based on the received radio frequency signal. The piezoelectric layer 128 enables the acoustic wave 412 to be formed in response to the alternating electric field generated by the interdigital transducers 304. In other words, the piezoelectric layer 128 at least partially enables the acoustic wave 412 to be formed in response to the electrical stimulation performed by one or more interdigital transducers 304.

[0073] Acoustic wave 412 is formed within piezoelectric layer 128 and interacts with IDT 304 or another IDT within electrode structure 302 ( Figure 4 The acoustic wave 412 formed may be a standing wave. In some implementations, two reflectors within the electrode structure 302 cause the acoustic wave 412 to be formed as a standing wave across a portion of the piezoelectric layer 128. In other implementations, the acoustic wave 412 propagates from the interdigital transducer 304 across the piezoelectric layer 128 to another interdigital transducer (not shown).

[0074] Using the piezoelectric effect, the electrode structure 302 generates a filtered RF signal based on the formed acoustic wave 412. Specifically, due to the mechanical stress generated by the propagation of the acoustic wave 412, the piezoelectric layer 128 generates an alternating electric field. The alternating electric field induces an alternating current in another interdigital transducer or the interdigital transducer 304. The alternating current forms a filtered RF signal provided at the output of the microacoustic filter 124. The filtered RF signal may include Figure 2 The filtered transmit signal 226 or the filtered receive signal 232 .

[0075] It should be understood that although Figure 4 A certain number of fingers are illustrated in the example, but the actual number of fingers and the length and width of the fingers and busbars may be different in actual implementations. Such parameters depend on the specific application and the desired filter characteristics. In addition, the microacoustic filter 124 may include a plurality of interconnected electrode structures 302, each of which includes a plurality of interdigital transducers 304 to achieve a desired passband (e.g., a plurality of interconnected resonators or interdigital transducers 304 connected in series or in parallel to form a desired filter transfer function).

[0076] Although not explicitly shown, the electrode structure 302 may also include two or more reflectors. In an example implementation, the interdigital transducer 304 is arranged between two reflectors (not shown). Each reflector within the electrode structure 302 may have a grating structure with two busbars and conductive fingers connected to the two busbars. In some implementations, the spacing of the reflectors may be similar or the same as the spacing 404 of the interdigital transducers 304. Figure 5 The characteristics of dielectric 130 are further described.

[0077] Figure 5 An example of an intermediate layer 312 and posts 314 of the dielectric 130 that partially suspends the piezoelectric layer 128 is illustrated. Figure 5 1 and 12. Dashed lines are illustrated in order to distinguish the intermediate layer 312 of the dielectric 130 from the pillars 314. The intermediate layer 312 covers or abuts at least a portion of the surface 402-1 of the piezoelectric layer 128. The first surface 502-1 of the intermediate layer 312 faces the base layer 126, while the second surface 502-2 of the intermediate layer 312 faces away from the base layer 126 (e.g., faces the piezoelectric layer 128). The second surface 502-2 of the intermediate layer 312 at least partially abuts the surface 402-1 of the piezoelectric layer 128. In general, the intermediate layer 312 represents a portion of the dielectric 130 disposed on the surface 402-1 of the piezoelectric layer 128 and / or disposed on the pillars 314.

[0078] The intermediate layer 312 can be implemented as one continuous component along the first (X) axis 406 and / or the second (Y) axis 408. Alternatively, the intermediate layer 312 can be implemented using multiple components that are physically separated from each other along the first (X) axis 406 and / or the second (Y) axis 408. Generally, the intermediate layer 312 is disposed on the pillars 314. In some cases, the intermediate layer 312 is also disposed on at least a portion of the electrode structure 302, such as across at least a portion of the fingers 310, at least a portion of the busbars 308, and / or at least a portion of the reflector or other portions of the chip. In an example implementation, the intermediate layer 312 is disposed across most of the length of the fingers 310.

[0079] The pillars 314 represent portions of the dielectric 130 disposed between the first surface 502-1 of the intermediate layer 312 and the base layer 126. Specifically, the pillars 314 include portions of the dielectric 130 that extend through a plane defined by the first surface 502-1 of the intermediate layer 312. In some implementations, the pillars 314 abut the base layer 126.

[0080] Generally, dielectric 130 includes three or more pillars 314. Pillars 314 are distributed at different points along first (X) axis 406. The position of one or more of pillars 314 along first (X) axis 406 may correspond to the position of one or more fingers 310. Sometimes, the number of pillars 314 is less than the number of fingers 310. In this case, pillars 314 may be positioned at points along first (X) axis 406 corresponding to a subset of fingers 310. The term "subset" may refer to a "proper subset" such that the subset may have fewer items than a set. Other times, the number of pillars 314 is at least equal to the number of fingers 310. In this case, the position of each finger 310 along first (X) axis 406 may be associated with the position of at least one pillar 314.

[0081] In the depicted configuration, the post 314 is positioned “under” at least a portion of the finger 310. In other words, the post 314 is positioned between the finger 310 and the base layer 126 along the third (Z) axis 410. Sometimes, the center point of the post 314 is aligned with the center point of the corresponding finger 310 along the third (Z) axis 410.

[0082] The post 314 can be implemented as one continuous component along the second (Y) axis 408. Alternatively, the post 314 can be implemented using multiple components that are physically separated from each other along the second (Y) axis 408. In some implementations, the length of the post 314 along the second (Y) axis 408 can be approximately equal to the length of the finger 310 (e.g., within + / - 10%, + / - 5%, + / - 3%, or + / - 2% of the length of the finger 310). In other implementations, the length of the post 314 along the second (Y) axis 408 is less than the length of the finger 310 but greater than half the length of the finger 310. In still other implementations, the length of the post 314 is greater than the length of the finger 310.

[0083] In the depicted configuration, the finger 310 of the electrode structure 302 is shown as having four surfaces 504-1, 504-2, 504-3, and 504-4. Although depicted as a rectangular cross-section, the cross-section of the finger 310 can be any shape, including a triangular shape or a rounded shape. Surfaces 504-1 and 504-2 can be substantially parallel to each other. In addition, surfaces 504-3 and 504-4 can be substantially parallel to each other and orthogonal to surfaces 504-1 and 504-2. Surface 504-1 faces the base layer 126 and can be in contact with the dielectric 130. Surface 504-2 is opposite to surface 504-1 and faces away from the base layer 126. Surface 504-2 is in contact with at least the piezoelectric layer 128. In some aspects, the third (Z) axis 410 is substantially orthogonal to surfaces 504-1 and 504-2. Surfaces 504-3 and 504-4 are adjacent to surfaces 504-1 and 504-2.The first (X) axis 406 may be substantially orthogonal to surfaces 504-3 and 504-4.

[0084] Although not explicitly shown, the electrode structure 302 may also have two other surfaces that are substantially orthogonal to the second (Y) axis 408. The dielectric 130 may optionally cover or abut at least a portion of these surfaces.

[0085] like Figure 5 As shown, surfaces 504-1, 504-3, and 504-4 of the finger 310 are in contact with the dielectric 130. In contrast, surface 504-2 of the finger 310 is in contact with surface 402-1 of the piezoelectric layer 128. In this way, the electrode structure 302 is at least partially embedded in the dielectric 130. Specifically, the electrode structure 302 is not buried in the piezoelectric layer 128. Even though the electrode structure 302 is embedded in the dielectric 130, the microacoustic filter 124 can meet the target electromechanical coupling coefficient (k 2 ). One way to define the electromechanical coupling coefficient is further shown in Equation 1 below:

[0086]

[0087] where f s is the resonant frequency, and f p is the anti-resonance frequency. As an example, the electromechanical coupling coefficient of the microacoustic filter 124 can be at least 25%. In order to improve the electromechanical coupling coefficient, the electrode structure 302 can be at least partially embedded in the piezoelectric layer 128, as described with respect to Figure 6 and Figure 7 as further described.

[0088] Figure 5 The micro-acoustic filter 124 is similar to Figure 4 The microacoustic filter 124 is similar to the microacoustic filter 124, except that the width of the cavity 316 is greater than the width of the gap between adjacent fingers 310. In other words, the width of the cavity 316 extends across the width of the gap. Explained in another way, the width of the post 314 is less than the width of the finger 310. For example, the width of the post 314 can be approximately equal to 75%, 50%, or 30% of the width of the finger 310. Generally speaking, the width of the cavity 316 is constrained by the target width of the post 314 to provide structural support for partially suspending the piezoelectric layer 128. The microacoustic filter 124 may also include additional layers, such as those described with respect to Figure 8 as further described.

[0089] Although not explicitly shown, dielectric 130 may be formed without cavities under busbars 308 or at outer edges of piezoelectric layer 128. In other words, dielectric 130 may be continuous across portions of piezoelectric layer 128 and / or portions of electrode structure 302 along third (Z) axis 410.

[0090] In an example implementation, the microacoustic filter 124 is designed to have a resonant frequency of approximately 4 GHz. The piezoelectric layer 128 may have a thickness of approximately 400 nanometers. The fingers 310 may have a thickness of approximately 100 nanometers. The thickness of the intermediate layer 312 between the surfaces 502-1 and 502-2 may be approximately 100 nanometers. The thickness of the pillars 314 may be approximately 100 nanometers. The width of the spacing 404 may be approximately 3.5 microns. The width of the fingers 310 along the first (X) axis 406 may be between approximately 100 nanometers and 2 microns. The width of the pillars 314 may be between approximately 100 nanometers and 2 microns. In general, the term "approximately" may mean that any dimension may be within + / -10% or less of the specified value (e.g., within + / -5%, + / -3%, or + / -2% of the specified value). With respect to Figures 6 to 8 Other example implementations of the microacoustic filter 124 are further described.

[0091] Figure 6 A second example implementation of a microacoustic filter 124 having a dielectric 130 that partially suspends a piezoelectric layer 128 is illustrated. Figure 6 The micro-acoustic filter 124 is similar to Figure 5The micro-acoustic filter 124, in addition to Figure 6 The fingers 310 are partially embedded in the dielectric 130, which is partially embedded in the piezoelectric layer 128. The surface 504-1 of each finger 310 is in contact with the dielectric 130, and the surface 504-2 of each finger 310 is in contact with the piezoelectric layer 128. In addition, the surfaces 504-3 and 504-4 are in contact with the dielectric 130 and the piezoelectric layer 128. By at least partially embedding the electrode structure 302 in the piezoelectric layer 128, Figure 5 Compared with the micro-acoustic filter 124, Figure 6 The micro-acoustic filter 124 may have a higher electromechanical coupling coefficient. In an exemplary embodiment, Figure 6 The electromechanical coupling coefficient of the microacoustic filter 124 may be about 30%.

[0092] Figure 7 A third example implementation of a microacoustic filter 124 having a dielectric 130 that partially suspends a piezoelectric layer 128 is illustrated. Figure 7 The micro-acoustic filter 124 is similar to Figure 5 and Figure 6 The micro-acoustic filter 124, in addition to Figure 7 The fingers 310 are at least partially embedded in the dielectric 130. Specifically, the electrode structure 302 is not buried in the dielectric 130. Therefore, the surface 502-1 of each finger 310 is in contact with the dielectric 130, and the surfaces 502-2 to 502-4 of each finger 310 are in contact with the piezoelectric layer 128. Figure 5 and Figure 6 Compared with the micro-acoustic filter 124, Figure 7 The microacoustic filter 124 may have a higher electromechanical coupling coefficient.

[0093] exist Figures 5 to 7 , the electrode structure 302 is shown in direct physical contact with the piezoelectric layer 128. In an alternative implementation, a dielectric layer (not shown) is present between the electrode structure 302 and the piezoelectric layer 128. The dielectric layer can be implemented using a material similar to or different from the dielectric 130. In an example implementation, the dielectric layer has a thickness of about 10 nanometers or less (e.g., 10 nanometers, 8 nanometers, 5 nanometers, or 2 nanometers). Generally speaking, the term "about" can mean that the thickness can be within + / -10% or less of a specified value (e.g., within + / -5%, + / -3%, or + / -2% of a specified value). The material and thickness of the dielectric layer can be tailored to achieve desired interface properties between the electrode structure 302 and the piezoelectric layer 128.

[0094] Figure 8 A fourth example implementation of a microacoustic filter 124 having a dielectric 130 that partially suspends a piezoelectric layer 128 is illustrated. Figure 8The micro-acoustic filter 124 may be similar to Figures 5 to 7 One or more additional layers are added to the micro-acoustic filter 124. The additional layers may include at least one dielectric layer 802, at least one acoustic mirror 804, at least one charge trapping layer 318, or some combination thereof.

[0095] In the depicted configuration, the dielectric layer 802 is disposed on the surface 402-2 of the piezoelectric layer 128. The dielectric layer 802 may further reduce the frequency temperature coefficient compared to other implementations of the microacoustic filter 124 that do not include the dielectric layer 802.

[0096] The acoustic reflector 804 is disposed between the dielectric 130 and the base layer 126. The acoustic reflector 804 includes a layer 806 having a first impedance and a layer 808 having a second impedance higher than the first impedance. In an example implementation, the layer 806 is implemented using silicon dioxide, and the layer 808 is implemented using tungsten (W). The acoustic reflector 804 can help confine the acoustic wave 412 to the piezoelectric layer 128. Although not explicitly shown, some example implementations of the micro-acoustic filter 124 may have multiple acoustic reflectors 804 stacked together between the dielectric 130 and the base layer 126.

[0097] The charge trapping layer 318 is typically disposed between the dielectric 130 and the base layer 126. In the depicted configuration, the charge trapping layer 318 is disposed between the acoustic mirror 804 and the base layer 126. Although not explicitly shown, some example implementations may include the charge trapping layer 318 and not include the acoustic mirror 804. In an example implementation, the charge trapping layer 318 is implemented using a polysilicon material. In general, the charge trapping layer 318 traps induced charges at the interface between the dielectric 130 and the base layer 126.

[0098] Fig. 9 1 is a flow chart illustrating an example process 900 for fabricating a microacoustic filter 124 having a dielectric with a partially suspended piezoelectric layer. The process 900 is described in terms of a set of blocks 902 to 908 that specify operations that may be performed. However, the operations are not necessarily limited to Fig. 9 The order shown or described in this article is not limited to the order shown in the figure or described in this article, because these operations can be implemented in an alternative order or in a completely or partially overlapping manner. In addition, more, fewer and / or different operations can be implemented to perform process 900 or alternative processes. The operations represented by the illustrated blocks of process 900 can be performed to produce (for example, Figure 1 3 ) micro-acoustic filter 124. More specifically, the operations of process 900 may be performed at least in part to use (e.g., Figures 4 to 8 The piezoelectric layer 128 is partially suspended by a dielectric 130.

[0099] At 902, a base layer is provided. For example, a manufacturing process provides base layer 126 such as Figures 4 to 8 As shown. The base layer 126 may have a single layer or multiple sub-layers. In an example implementation, the base layer 126 is implemented using silicon to provide isolation.

[0100] At 904, a piezoelectric layer is provided. For example, the manufacturing process provides the piezoelectric layer 128, such as Figures 4 to 8 The piezoelectric layer 128 can be implemented using materials such as lithium niobate, lithium tantalate, quartz, aluminum nitride, scandium aluminum nitride, or some combination thereof. In some aspects, the structure of the piezoelectric layer 128 is tailored so that the piezoelectric layer 128 can excite a plate mode, such as an antisymmetric plate mode.

[0101] At 906, an electrode structure having a plurality of fingers arranged across a plane is provided. The plane is defined by a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers. The electrode structure is in contact with the piezoelectric layer. For example, the manufacturing process provides the electrode structure 302, such as Figures 4 to 8 shown.

[0102] Electrode structure 302 includes a plurality of fingers 310 arranged across a plane defined by a first (X) axis 406 and a second (Y) axis 408. The first (X) axis is substantially perpendicular to the fingers 310 and parallel to the direction of acoustic wave propagation. The second (Y) axis is substantially parallel to the fingers 310. Electrode structure 302 may be formed using a conductive material such as a metal.

[0103] In some example implementations, the electrode structure 302 is disposed on a second surface 402-2 of the piezoelectric layer 128 that faces away from the base layer 126. In other example implementations, the electrode structure 302 is disposed between the piezoelectric layer 128 and the dielectric 130. This enables the second surface 402-2 of the piezoelectric layer 128 to be trimmed after manufacturing the electrode structure 302. In both example implementations, the electrode structure 302 is in contact with the piezoelectric layer 128. Thus, the electrode structure 302 may optionally be in contact with the dielectric 130.

[0104] At 908, a dielectric is provided that separates the piezoelectric layer from the base layer. The dielectric defines a cavity between the piezoelectric layer and the base layer and supports the piezoelectric layer across at least three points along the first axis. For example, the manufacturing process provides a dielectric 130 that separates the piezoelectric layer 128 from the base layer 126, such as Figures 4 to 8The dielectric 130 defines a cavity 316 between the piezoelectric layer 128 (e.g., a portion of the piezoelectric layer 128 covered by the dielectric 130) and the base layer 126 along the third (Z) axis 410. In some implementations, the cavity 316 is positioned below the gap between adjacent fingers 310 of the electrode structure 302. Optionally, the manufacturing process may further provide at least one dielectric layer 802, at least one acoustic reflector 804, and at least one ( Figure 6 ) charge trapping layer 318 or some combination thereof.

[0105] There are various processes for implementing microacoustic filter 124. In this case, the manufacturing process may deposit electrode structure 302 on piezoelectric layer 128. Next, the manufacturing process may provide dielectric 130 by depositing intermediate layer 312 across piezoelectric layer 128 and electrode structure 302 and depositing pillars 314 on intermediate layer 312. Pillars 314 may be bonded to base layer 126.

[0106] Alternatively, the microacoustic filter 124 can be manufactured using an etching process. The example manufacturing process deposits a sacrificial layer across the intermediate layer 312 and the posts 314 before bonding the posts 314 to the base layer 126. After bonding the posts 314 and the sacrificial layer to the base layer 126, the manufacturing process uses access holes at the front or back of the microacoustic filter 124 to release the sacrificial layer via etching.

[0107] As an alternative to using bonding, another example manufacturing process sequentially deposits Figure 5 Each layer of the microacoustic filter 124 of the manufacturing process. For example, the manufacturing process deposits a sacrificial layer on the base layer 126. The manufacturing process also deposits the dielectric 130 on the sacrificial layer. A metal damascene process can be performed to partially embed the electrode structure 302 within the dielectric 130. The manufacturing process also deposits the piezoelectric layer 128 on the surface of the dielectric 130 and the electrode structure 302. The manufacturing process uses etching to release the sacrificial layer.

[0108] In the case where the electrode structure 302 is disposed on the surface 402 - 1 of the piezoelectric layer 128 , the above manufacturing process may also grind, polish and / or trim the surface 402 - 2 of the piezoelectric layer 128 .

[0109] Some aspects are described below.

[0110] Aspect 1: A device, comprising:

[0111] A micro-acoustic filter, the micro-acoustic filter comprising:

[0112] basal layer;

[0113] Piezoelectric layer;

[0114] an electrode structure in contact with the piezoelectric layer, the electrode structure comprising a plurality of fingers arranged across a plane having a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers; and

[0115] A dielectric, the dielectric being configured to:

[0116] separating the piezoelectric layer from the substrate layer;

[0117] A cavity is defined between the piezoelectric layer and the base layer; and the piezoelectric layer is supported across at least three points along the first axis.

[0118] Aspect 2: The apparatus of aspect 1, wherein the dielectric is configured to define the cavity between the base layer and at least a portion of the dielectric.

[0119] Aspect 3: The apparatus according to aspect 1 or 2, wherein one or more of the at least three points correspond to the position of one or more of the plurality of fingers along the first axis.

[0120] Aspect 4: The apparatus of aspect 3, wherein the one or more fingers comprise a subset of the plurality of fingers.

[0121] Aspect 5: The apparatus of aspect 4, wherein the plurality of fingers comprises all fingers of the electrode structure.

[0122] Aspect 6: The device of any preceding aspect, wherein the dielectric and the piezoelectric layer are adhered together.

[0123] Aspect 7: The apparatus according to any of the preceding aspects, wherein:

[0124] The piezoelectric layer has a surface facing the base layer; and

[0125] The dielectric includes:

[0126] an intermediate layer disposed across the surface of the piezoelectric layer, the intermediate layer having a surface facing the substrate layer; and

[0127] At least three posts extend through a plane defined by the surface of the intermediate layer and toward the base layer to define the cavity between the intermediate layer and the base layer, the at least three posts being positioned at the at least three points along the first axis.

[0128] Aspect 8: The device of aspect 7, wherein one of the at least three pillars is positioned between one of the plurality of fingers and the base layer along a third axis perpendicular to the first axis and the second axis.

[0129] Aspect 9: The apparatus according to aspect 8, wherein:

[0130] The width of the post is less than the width of the finger; and

[0131] The length of the post is approximately equal to the length of the finger.

[0132] Aspect 10: The apparatus according to any of the preceding aspects, wherein:

[0133] The electrode structure is at least partially embedded in the dielectric; and

[0134] A surface of the electrode structure faces away from the base layer and is in contact with a surface of the piezoelectric layer facing the base layer.

[0135] Aspect 11: The device of any one of aspects 1 to 9, wherein the electrode structure is partially embedded within the dielectric and partially embedded within the piezoelectric layer.

[0136] Aspect 12: The device according to any one of aspects 1 to 9, wherein:

[0137] The electrode structure is at least partially embedded in the piezoelectric layer; and

[0138] A surface of the electrode structure faces the base layer and is in contact with a surface of the dielectric facing away from the base layer.

[0139] Aspect 13: The device according to any one of aspects 1 to 9, wherein the electrode structure is disposed on a surface of the piezoelectric layer facing away from the substrate layer.

[0140] Aspect 14: The apparatus according to any of the preceding aspects, wherein:

[0141] The cavity is at least partially filled with a gas; and

[0142] The gas includes air.

[0143] Aspect 15: The device according to any preceding aspect, wherein the dielectric comprises one or more of the following:

[0144] Silicon dioxide;

[0145] Doped silica;

[0146] Silicon nitride;

[0147] Aluminium oxide; or

[0148] Aluminum Nitride.

[0149] Aspect 16: The device of any preceding aspect, wherein the dielectric has a thickness between approximately fifty nanometers and two micrometers.

[0150] Aspect 17: The device according to any preceding aspect, wherein the piezoelectric layer is configured to excite an antisymmetric plate mode.

[0151] Aspect 18: The device according to any preceding aspect, further comprising a dielectric layer disposed on a surface of the piezoelectric layer facing away from the base layer.

[0152] Aspect 19: The device according to any preceding aspect, further comprising at least one acoustic mirror disposed between the dielectric and the base layer.

[0153] Aspect 20: The device of any preceding aspect, further comprising a charge trapping layer disposed between the dielectric and the base layer.

[0154] Aspect 21: The apparatus according to any preceding aspect, wherein:

[0155] The microacoustic filter includes a plurality of cascaded resonators; and

[0156] A resonator in the plurality of cascaded resonators includes the base layer, the piezoelectric layer, the electrode structure, and the dielectric.

[0157] Aspect 22: The apparatus according to any of the preceding aspects, further comprising:

[0158] A wireless transceiver coupled to at least one antenna, the wireless transceiver including the microacoustic filter and configured to use the microacoustic filter to filter wireless signals communicated via the at least one antenna.

[0159] Aspect 23: A device, comprising:

[0160] A micro-acoustic filter, the micro-acoustic filter being configured to generate a filtered signal from a radio frequency signal, the micro-acoustic filter comprising:

[0161] means for converting the radio frequency signal into an acoustic wave and converting the resulting acoustic wave into the filtered signal;

[0162] means for exciting the antisymmetric plate modes to produce said formed acoustic waves,

[0163] means for confining energy of said antisymmetric plate mode within said means for exciting; and

[0164] Means for partially suspending the means for excitation from the means for limiting energy.

[0165] Aspect 24: The apparatus according to Aspect 23, wherein:

[0166] The means for converting comprises means for generating an electric field in a direction parallel to the first axis; and

[0167] The means for partially suspending comprises:

[0168] means for defining a cavity between said means for energizing and said means for confining energy; and

[0169] Means for supporting the means for excitation across at least three points along the first axis.

[0170] Aspect 25: A method for manufacturing a microacoustic filter, the method comprising:

[0171] Provides a base layer;

[0172] providing a piezoelectric layer;

[0173] providing an electrode structure having a plurality of fingers arranged across a plane defined by a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers, the electrode structure contacting the piezoelectric layer; and

[0174] A dielectric is provided that separates the piezoelectric layer from the base layer, defines a cavity between the piezoelectric layer and the base layer, and supports the piezoelectric layer across at least three points along the first axis.

[0175] Aspect 26: The method according to Aspect 25, wherein:

[0176] Providing the electrode structure includes providing the electrode structure so that the electrode structure is in contact with a first surface of the piezoelectric layer facing the base layer, and

[0177] The method further comprises:

[0178] A second surface of the piezoelectric layer opposite the first surface is trimmed.

[0179] Aspect 27: A microacoustic filter, the microacoustic filter comprising:

[0180] an electrode structure comprising a plurality of fingers arranged across a plane having a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers;

[0181] basal layer;

[0182] a piezoelectric layer having a surface facing the base layer; and

[0183] A dielectric, the dielectric comprising:

[0184] an intermediate layer disposed across the surface of the piezoelectric layer, the intermediate layer having a surface facing the base layer; and

[0185] At least three posts extend through a plane defined by the surface of the intermediate layer and toward the base layer to define a cavity between the intermediate layer and the base layer, the at least three posts being positioned across at least three points along the first axis.

[0186] Aspect 28: The microacoustic filter according to Aspect 27, wherein the electrode structure is positioned on a side of the piezoelectric layer facing the substrate layer.

[0187] Aspect 29: The microacoustic filter according to Aspect 27 or 28, wherein the piezoelectric layer has a crystal structure for exciting a plate mode.

[0188] Aspect 30: The micro-acoustic filter according to Aspect 29, wherein:

[0189] a third axis orthogonal to the first axis and the second axis;

[0190] The first axis, the second axis, and the third axis are oriented relative to the crystal structure of the piezoelectric layer defined by Euler angles λ, μ, and θ; and

[0191] The piezoelectric layer comprises:

[0192] Lithium niobate, wherein the value of the Euler angle λ is about 0°, the value of the Euler angle μ is about 38°, and the value of the Euler angle θ is about 0°;

[0193] The lithium niobate, wherein the value of the Euler angle λ is about 0°, the value of the Euler angle μ is about 0°, and the value of the Euler angle θ is about 90°; or

[0194] Lithium tantalate, wherein the value of the Euler angle λ is about 0°, the value of the Euler angle μ is about 42°, and the value of the Euler angle θ is about 0°.

[0195] Unless the context dictates otherwise, the use of the word "or" herein may be considered an "inclusive or" or use of a term that allows inclusion or application of one or more items linked by the word "or" (e.g., the phrase "A or B" may be interpreted as allowing only "A", only "B", or both "A" and "B"). As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items (including a single member). As an example, "at least one of a, b, or c" is intended to cover: a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c). In addition, the items represented in the drawings and the terms discussed herein may indicate one or more items or terms, and thus the singular or plural forms of those items and terms may be referred to interchangeably in this written description. Finally, although the subject matter has been described in language specific to structural features or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including not necessarily being limited to the organization in which the features are arranged or the order in which the operations are performed.

Claims

1. A device, comprising: A micro-acoustic filter, the micro-acoustic filter comprising: basal layer; Piezoelectric layer; an electrode structure in contact with the piezoelectric layer, the electrode structure comprising a plurality of fingers arranged across a plane having a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers; and A dielectric, the dielectric being configured to: separating the piezoelectric layer from the substrate layer; defining a cavity between the piezoelectric layer and the substrate layer; and The piezoelectric layer is supported across at least three points along the first axis. 2 . The apparatus of claim 1 , wherein the dielectric is configured to define the cavity between the base layer and at least a portion of the dielectric. 3 . The apparatus of claim 1 , wherein one or more of the at least three points correspond to positions of one or more of the plurality of fingers along the first axis. The apparatus of claim 3 , wherein the one or more fingers comprise a subset of the plurality of fingers.

5. The apparatus of claim 4, wherein the plurality of fingers comprises all fingers of the electrode structure.

6. The device of claim 1, wherein the dielectric and the piezoelectric layer are adhered together.

7. The device according to claim 1, wherein: The piezoelectric layer has a surface facing the base layer; and The dielectric includes: an intermediate layer disposed across the surface of the piezoelectric layer, the intermediate layer having a surface facing the substrate layer; as well as At least three posts extend through a plane defined by the surface of the intermediate layer and toward the base layer to define the cavity between the intermediate layer and the base layer, the at least three posts being positioned at the at least three points along the first axis.

8. The device of claim 7, wherein one of the at least three posts is positioned between one of the plurality of fingers and the base layer along a third axis perpendicular to the first axis and the second axis.

9. The device according to claim 8, wherein: The width of the post is less than the width of the finger; and The length of the post is approximately equal to the length of the finger.

10. The device according to claim 1, wherein: The electrode structure is at least partially embedded in the dielectric; and A surface of the electrode structure faces away from the base layer and is in contact with a surface of the piezoelectric layer facing the base layer.

11. The device of claim 1, wherein the electrode structure is partially embedded within the dielectric and partially embedded within the piezoelectric layer.

12. The device according to claim 1, wherein: The electrode structure is at least partially embedded in the piezoelectric layer; and A surface of the electrode structure faces the base layer and is in contact with a surface of the dielectric facing away from the base layer.

13. The device according to claim 1, wherein the electrode structure is disposed on a surface of the piezoelectric layer facing away from the substrate layer.

14. The device according to claim 1, wherein: The cavity is at least partially filled with a gas; and The gas includes air.

15. The device of claim 1, wherein the dielectric comprises one or more of: Silicon dioxide; Doped silica; Silicon nitride; Aluminium oxide; or Aluminum Nitride.

16. The device of claim 1, wherein the dielectric has a thickness between approximately fifty nanometers and two microns.

17. The apparatus of claim 1, wherein the piezoelectric layer is configured to excite an antisymmetric plate mode.

18. The device of claim 1, further comprising a dielectric layer disposed on a surface of the piezoelectric layer facing away from the substrate layer.

19. The device of claim 1, further comprising at least one acoustic mirror disposed between the dielectric and the base layer.

20. The device of claim 1, further comprising a charge trapping layer disposed between the dielectric and the base layer.

21. The apparatus of claim 1, wherein: The microacoustic filter includes a plurality of cascaded resonators; and A resonator in the plurality of cascaded resonators includes the base layer, the piezoelectric layer, the electrode structure, and the dielectric.

22. The apparatus according to claim 1, further comprising: A wireless transceiver coupled to at least one antenna, the wireless transceiver including the microacoustic filter and configured to use the microacoustic filter to filter wireless signals communicated via the at least one antenna.

23. A device, comprising: A micro-acoustic filter, the micro-acoustic filter being configured to generate a filtered signal from a radio frequency signal, the micro-acoustic filter comprising: means for converting the radio frequency signal into an acoustic wave and converting the resulting acoustic wave into the filtered signal; means for exciting the antisymmetric plate modes to produce said formed acoustic waves, means for confining energy of said antisymmetric plate mode within said means for exciting; and Means for partially suspending the means for excitation from the means for limiting energy.

24. The apparatus of claim 23, wherein: The means for converting includes means for generating an electric field in a direction parallel to the first axis; and The means for partially suspending comprises: means for defining a cavity between said means for energizing and said means for confining energy; and Means for supporting the means for excitation across at least three points along the first axis.

25. A method for manufacturing a microacoustic filter, the method comprising: Provides a base layer; providing a piezoelectric layer; providing an electrode structure having a plurality of fingers arranged across a plane defined by a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers, the electrode structure contacting the piezoelectric layer; as well as A dielectric is provided that separates the piezoelectric layer from the base layer, defines a cavity between the piezoelectric layer and the base layer, and supports the piezoelectric layer across at least three points along the first axis.

26. The method of claim 25, wherein: Providing the electrode structure includes providing the electrode structure so that the electrode structure is in contact with a first surface of the piezoelectric layer facing the base layer, and The method further comprises: A second surface of the piezoelectric layer opposite the first surface is trimmed.

27. A microacoustic filter, comprising: an electrode structure comprising a plurality of fingers arranged across a plane having a first axis perpendicular to the plurality of fingers and a second axis parallel to the plurality of fingers; basal layer; a piezoelectric layer having a surface facing the base layer; and A dielectric, the dielectric comprising: an intermediate layer disposed across the surface of the piezoelectric layer, the intermediate layer having a surface facing the substrate layer; and At least three posts extend through a plane defined by the surface of the intermediate layer and toward the base layer to define a cavity between the intermediate layer and the base layer, the at least three posts being positioned across at least three points along the first axis.

28. The microacoustic filter according to claim 27, wherein the electrode structure is positioned on a side of the piezoelectric layer facing the substrate layer.

29. The microacoustic filter according to claim 27, wherein the piezoelectric layer has a crystal structure for exciting a plate mode.

30. The microacoustic filter according to claim 29, wherein a third axis orthogonal to the first axis and the second axis; The first axis, the second axis, and the third axis are oriented relative to the crystal structure of the piezoelectric layer defined by Euler angles λ, μ, and θ; and The piezoelectric layer comprises: Lithium niobate, wherein the value of the Euler angle λ is about 0°, the value of the Euler angle μ is about 38°, and the value of the Euler angle θ is about 0°; The lithium niobate, wherein the value of the Euler angle λ is about 0°, the value of the Euler angle μ is about 0°, and the value of the Euler angle θ is about 90°; or Lithium tantalate, wherein the value of the Euler angle λ is about 0°, the value of the Euler angle μ is about 42°, and the value of the Euler angle θ is about 0°.

Images