Electroacoustic device with electrically conductive acoustic mirror

Abstract

Certain aspects of the present disclosure can be implemented in an electro-acoustic device. The electro-acoustic device generally includes a substrate, a bottom electrode layer disposed above the substrate, an acoustic mirror stack having a dielectric layer disposed above the bottom electrode layer and a conductive layer disposed above the dielectric layer, a piezoelectric layer disposed above the acoustic mirror stack, and one or more vias disposed between the bottom electrode layer and the conductive layer, the one or more vias electrically coupling the bottom electrode layer and the conductive layer.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 106,727, filed October 28, 2020, which is expressly incorporated by reference herein in its entirety as if fully set forth below and for all applicable purposes. TECHNICAL FIELD

[0003] Aspects of the present disclosure relate to electronic devices, and more particularly to electro-acoustic devices. BACKGROUND

[0004] Electronic devices include conventional computing devices such as desktop computers, notebook computers, tablet computers, smartphones, wearable devices such as smartwatches, Internet servers, and the like. These various electronic devices provide information, entertainment, socialization, protection, security, productivity, transportation, manufacturing, and other services to human users. Many of the functions of these various 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, broadcast, and the like. Wireless communication devices can transmit and / or receive radio frequency (RF) signals via any of a variety of suitable radio access technologies (RATs) including, but not limited to, 5G New Radio (NR), Long-Term Evolution (LTE), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Wideband CDMA (WCDMA), Global System for Mobile (GSM), Bluetooth, Bluetooth Low Energy (BLE), ZigBee, Wireless Local Area Network (WLAN) RATs (e.g., IEEE 802.11), and the like.

[0005] Wireless communication transceivers used in these electronic devices often include multiple radio frequency (RF) filters that are used to filter signals of particular frequencies or frequency ranges. In many applications, electro-acoustic devices (e.g., “acoustic filters”) are used to filter high frequency (e.g., typically greater than 500 MHz) signals. Using a piezoelectric material as a vibration medium, an acoustic resonator operates by converting an electrical signal wave propagating along an electrical conductor into an acoustic wave propagating via the piezoelectric material. The acoustic wave propagates at a speed that is significantly smaller in magnitude than the speed of propagation of electromagnetic waves. Generally, the speed of propagation of a wave is proportional in magnitude to the wavelength of the wave. Thus, 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 enables filtering to be performed using smaller filter devices. This allows acoustic resonators to be used in electronic devices that have size limitations, such as the electronic devices listed above (e.g., including particularly portable electronic devices such as cellular telephones).

[0006] As the number of frequency bands used in wireless communications increases and as the desired frequency bands of filters widen, the performance of acoustic filters is critical to reducing resistive losses, increasing attenuation of out-of-band signals, and improving the overall performance of electronic devices. As such, acoustic filters with improved performance are in demand. SUMMARY

[0007] The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. The features described herein will become more fully apparent in light of the following detailed description, taken in conjunction with the accompanying figures, in which:

[0008] Certain aspects of the present disclosure can be implemented in an electroacoustic device. The electroacoustic device generally includes a substrate; a bottom electrode layer disposed above the substrate; an acoustic mirror stack having a first dielectric layer disposed above the bottom electrode layer and a first conductive layer disposed above the first dielectric layer; a piezoelectric layer disposed above the acoustic mirror stack; and one or more first vias disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and the first conductive layer.

[0009] Certain aspects of the present disclosure can be implemented in a method for signal processing. The method generally includes receiving a signal at a terminal of an electroacoustic device and processing the signal via the electroacoustic device. The electroacoustic device includes a substrate; a bottom electrode layer disposed above the substrate; an acoustic mirror stack having a first dielectric layer disposed above the bottom electrode layer and a first conductive layer disposed above the first dielectric layer; a piezoelectric layer disposed above the acoustic mirror stack; and one or more first vias disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and the first conductive layer.

[0010] Certain aspects of the present disclosure relate to a method of manufacturing an electroacoustic device. The method generally includes forming a bottom electrode layer above a substrate; forming an acoustic mirror stack including: (a) a first dielectric layer disposed above the bottom electrode layer; and (b) a first conductive layer disposed above the first dielectric layer; forming one or more first vias electrically coupled between the bottom electrode layer and the first conductive layer; and forming a piezoelectric layer above the acoustic mirror stack.

[0011] To the accomplishment of the foregoing and related ends, one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more aspects. These aspects are indicative, however, of but a few of the various ways in which principles of the aspects can be employed. Other aspects can employ each of the features noted in connection with the described aspects, throughout the specification. BRIEF DESCRIPTION OF DRAWINGS

[0012] For a detailed understanding of the above-described features of the present disclosure, reference can be made to the following detailed description and accompanying drawings that set forth a certain understanding of the aspects (some of which are set forth above in the Summary). It should be noted, however, that the Figures are merely meant to illustrate only certain exemplary aspects of the present disclosure and therefore should not be taken to limit its scope as the specification can allow for other equally effective aspects.

[0013] Figure 1A FIG. 1 is a diagram conceptually illustrating an example electroacoustic device according to certain aspects of the present disclosure.

[0014] Figure 1B FIG. 2 is a diagram illustrating a cross-section of an example electroacoustic device according to certain aspects of the present disclosure. Figure 1A

[0015] Figure 2 FIG. 3 is a diagram illustrating a cross-section of an example electroacoustic device implemented with vias through a reflective layer according to certain aspects of the present disclosure.

[0016] Figure 3 FIG. 4 is a schematic diagram of an example electroacoustic filter circuit that can include an electroacoustic device according to certain aspects of the present disclosure. Figure 2

[0017] FIG. 5 is a flow diagram illustrating example operations for manufacturing an electroacoustic device according to certain aspects of the present disclosure. Figures 4A to 4I

[0018] FIG. 6 is a flow diagram illustrating example operations for signal processing according to certain aspects of the present disclosure. Figure 5

[0019] FIG. 7 is a diagram of an example transceiver in which an electroacoustic filter can be employed according to certain aspects of the present disclosure. Figure 6 Figure 3 FIG. 8 is a diagram of a wireless communication network including wireless communication devices that include transceivers, such as transceivers having electroacoustic filters, according to certain aspects of the present disclosure.

[0020] Figure 7 Figure 6 FIG. 9 is a flow diagram illustrating example operations for manufacturing an electroacoustic device according to certain aspects of the present disclosure.

[0021] Figure 8 FIG. 10 is a flow diagram illustrating example operations for signal processing according to certain aspects of the present disclosure.

[0022] ​​​For ease of understanding, the same reference numbers will be used in different drawings to designate the same elements common to the drawings. It is contemplated that elements disclosed in one aspect can be beneficially utilized on other aspects without specific recitation. DETAILED DESCRIPTION

[0023] Aspects of the disclosure provide an electro-acoustic device having a via through a reflective layer of an acoustic mirror to allow a bottom electrode (BE) of the electro-acoustic device to be implemented below the reflective layer.

[0024] Electro-acoustic devices, such as bulk acoustic wave (BAW) resonators, which employ a piezoelectric material arranged between electrode structures, are designed to cover a wider frequency range (e.g., 500 MHz to 7 GHz), have a higher bandwidth (e.g., up to 20%), and have improved efficiency and performance. Generally, a BAW resonator is an electromechanical device in which a standing wave is generated in a body of piezoelectric material arranged between electrodes to which an electrical signal is applied. One type of BAW resonator is referred to as a film bulk acoustic resonator (FBAR). An FBAR can include a piezoelectric material fabricated by a thin film process that is sandwiched between two electrodes and acoustically isolated from the surrounding medium. A solidly mounted resonator (SMR) is a type of BAW resonator that has a piezoelectric film sandwiched between two electrodes and a Bragg reflector having alternating high and low acoustic impedance layers of quarter- wavelength thickness.

[0025] In some implementations (e.g., using an SMR), the BE is implemented between one or more reflective layers and the piezoelectric layer. The BE can be implemented as a relatively thin layer. As a result, the electrical losses associated with the thin BE can degrade the performance and power durability of the electro-acoustic device. In other words, the connection to the BE can be primarily implemented through aluminum copper (AlCu), and because Al is an acoustically lossy material, can be implemented as a relatively thin layer. The self-heating of the electro-acoustic device further increases the resistance of the BE.

[0026] Certain aspects of the disclosure relate to techniques for implementing the BE below the reflective layer, which allows for increasing the thickness of the BE compared to conventional implementations. Increasing the thickness of the BE can reduce the resistivity of the BE, thereby improving the performance and power durability of the electro-acoustic device. The electro-acoustic devices provided herein reduce electrical and acoustic losses, provide higher acoustic reflection, and reduce the frequency temperature coefficient (TCF) and electrical conductance of the electro-acoustic device compared to conventional implementations. Electrical coupling between the BE and the piezoelectric layer can be facilitated through a via through the reflective layer, as described in greater detail herein.

[0027] Example Electro-Acoustic Devices

[0028] Figure 1AA conceptual cross-section of an example electro-acoustic device 100 is shown in accordance with certain aspects of the present disclosure. The electro-acoustic device 100 can be configured as, or be part of, a BAW resonator. In certain cases, a wireless communication device can include a BAW resonator, e.g., as described herein with respect to Figure 3 、 Figure 6 、 Figure 7 and Figure 8 further described.

[0029] As shown, the electro-acoustic device 100 includes an electrode structure 102 (e.g., also referred to as a top electrode (TE)), a piezoelectric layer 104, an electrode structure 106 (e.g., also referred to as a bottom electrode (BE)), one or more reflective layers 108, and a substrate 110. In certain aspects of the present disclosure, the one or more reflective layers 108 can be disposed between the electrode structure 106 and the piezoelectric layer 104. One or more vias (not shown in FIG. 1) can be implemented through the one or more reflective layers 108 to allow the electrode structure 106 to electrically extend to the piezoelectric layer 104. Figure 1A

[0030] The electrode structure 102 can be disposed above the piezoelectric layer 104. The electrode structure 102 can include an electrically conductive material, such as a metal or metal alloy including aluminum (Al), chromium (Cr), cobalt (Co), copper (Cu), gold (Au), molybdenum (Mo), platinum (Pt), ruthenium (Ru), tantalum (Ta), titanium (Ti), tungsten (W), combinations thereof (e.g., AlCu), or any other suitable material. In certain cases, the electrically conductive material can include graphene or other electrically conductive non-metallic material. The piezoelectric layer 104 can include a piezoelectric material, such as aluminum nitride (AIN), zinc oxide (ZnO), a quartz crystal such as lithium tantalate (LiTa03) or lithium niobate (LiNb03), a doped variant of the foregoing, or other suitable piezoelectric material.

[0031] The electrode structure 106 can include an electrically conductive material, such as a metal or metal alloy, as described herein with respect to the electrode structure 102. In certain aspects, the electrode structure 106 can have the same shape, size, and structure as the electrode structure 102. For example, the electrode structures 102, 106 can both be electrode plates. In certain cases, the electrode structure 106 can have a different form, size, or structure than the electrode structure 102.

[0032] The one or more reflective layers 108 can function as a Bragg reflector to acoustically isolate the BAW resonator from the substrate 110, or at least reduce acoustic coupling between the BAW resonator and the substrate 110. Generally, the one or more reflective layers 108 can include alternating layers of a material having a low acoustic impedance and a material having a high acoustic impedance, as described herein with respect to Figure 1B further described.​

[0033] Substrate 110 can be disposed below one or more reflective layers 108 such that substrate 110 is disposed below electrode structure 102 and electrode structure 106. Substrate 110 can serve as a carrier for the BAW resonator. In some aspects, substrate 110 can be formed from a semiconductor wafer such as a silicon (Si) wafer. Substrate 110 can include any of a variety of other suitable materials such as aluminum oxide, glass, or sapphire.

[0034] An electrical signal (e.g., an applied AC voltage) excited between electrode structures 102 and 106 is transduced into an acoustic wave 112 propagating in piezoelectric layer 104. That is, the application of an electrical signal to piezoelectric layer 104 through electrode structures 102 and 106 converts the electrical signal into an acoustic wave 112 in piezoelectric layer 104. At certain frequencies, a resonant or anti-resonant mechanical standing wave can be formed, thereby enabling a filter function. To avoid leakage into the substrate, a reflective layer can be disposed below the electro-acoustic resonator. One or more reflective layers 108 can also reflect acoustic waves 114 back into piezoelectric layer 104 and electrode structure 102 with high acoustic reflectivity. The reflected acoustic waves 114 can improve the efficiency of the BAW resonator and acoustically decouple substrate 110 from the BAW resonator. In many applications, piezoelectric layer 104 has a particular crystal orientation such that when electrode structure 102 is arranged with respect to the crystal orientation of piezoelectric layer 104, the acoustic wave propagates primarily in a direction from electrode structure 102 to electrode structure 106.

[0035] Figure 1B An example layer of one or more reflective layers 108 of electro-acoustic device 100 is shown in accordance with certain aspects of the disclosure.

[0036] In this example, one or more reflective layers 108 include reflective layer 116, reflective layer 118, reflective layer 120, and reflective layer 122. In certain cases, one or more reflective layers 108 can have any suitable number of reflective layers, such as fewer or more than the four reflective layers as shown in this example. Reflective layer 116 and reflective layer 120 can include a material having a higher acoustic impedance than the material of reflective layer 118 and reflective layer 122. For example, reflective layer 118 and reflective layer 122 can include silicon dioxide (SiO2), while reflective layer 116 and reflective layer 120 can include tungsten (W) or other suitable material having a higher acoustic impedance than silicon dioxide or aluminum nitride.

[0037] The one or more reflective layers 108 can have the same thickness (e.g., a quarter wavelength (A / 4) thickness according to a range of operating frequencies of the electroacoustic device 100) or different thicknesses. Although in this example, the one or more reflective layers 108 are depicted as having the same length, the lengths of the one or more reflective layers 106 can vary (i.e., individual layers can have different lengths).

[0038] Figure 2 A cross-section of an example electroacoustic device 200 implemented with vias through reflective layers is shown in accordance with certain aspects of the present disclosure. The electroacoustic device 200 can include a dielectric region 250 (e.g., composed of Si02), as shown, where the reflective layers 118, 122 are part of the dielectric region 250. In addition, a dielectric layer 260 (e.g., composed of Si02) can be included between the electrode structure 106 and the substrate 110 (e.g., part of a silicon (Si) wafer). The electroacoustic device can include vias 206, 208, 210 through the reflective layer 118. Although Figure 2 Three vias are shown through each layer (e.g., the reflective layer 122) for ease of understanding, but any number of vias less than three or greater than three can be implemented. Since the reflective layer 118 is implemented using a dielectric (e.g., Si02), the vias 206, 208, 210 through the reflective layer 118 facilitate electrical coupling between the reflective layers 116, 120 implemented using a conductive material (e.g., W). In some aspects, vias 212, 214, 216 can also be formed through the reflective layer 122 (e.g., also composed of Si02) to facilitate electrical coupling between the electrode structure 106 and the reflective layer 120. Optionally, a reflective layer 202 can be implemented between the electrode structure 106 and the reflective layer 122, as shown.

[0039] By forming the vias 206, 208, 210, 212, 214, 216, the electrode structure 106 can be implemented below the reflective layers to allow the electrode structure 106 to be implemented as a thicker electrode layer compared to conventional implementations where the electrode structure is implemented above the reflective layers. For example, the electrode structure 106 can have a thickness greater than 100 nm (e.g., 1000 nm) to reduce the resistivity of the electrode structure 106 compared to conventional implementations.

[0040] Figure 3This is a schematic diagram of an electroacoustic filter circuit 300 that may include an electroacoustic device 200, according to certain aspects of this disclosure. The filter circuit 300 provides an example of the use of the electroacoustic device 200. The filter circuit 300 includes an input terminal 302 and an output terminal 314. Between the input terminal 302 and the output terminal 314, a ladder network of electroacoustic devices (e.g., BAW resonators) is provided. The filter circuit 300 includes a first BAW resonator 304, a second BAW resonator 306, and a third BAW resonator 308, all of which are connected in series between the input terminal 302 and the output terminal 314. A fourth BAW resonator 310 (e.g., a shunt resonator) has a first terminal connected between the first BAW resonator 304 and the second BAW resonator 306 and a second terminal connected to a ground potential node. The fifth BAW resonator 312 (e.g., a shunt resonator) has a first terminal connected between the second BAW resonator 306 and the third BAW resonator 308 and a second terminal connected to a ground potential node. The electroacoustic filter circuit 300 may be, for example, a bandpass circuit with a selected frequency range (e.g., between 500 MHz and 7 GHz).

[0041] Figures 4A to 4I Example operations for manufacturing an electroacoustic device 200 according to certain aspects of this disclosure are shown. For example... Figure 4A As shown, a dielectric layer 260 (e.g., composed of SiO2), an electrode structure 106 (e.g., composed of AlCu), and a reflective layer 202 (e.g., composed of W) can be formed over a substrate 110 (e.g., a portion of a Si wafer). Figure 4B As shown, a conductive layer 402 (e.g., composed of W) can be formed above the reflective layer 202, and this conductive layer 402 can be used to form vias 212, 214, and 216 using photolithography or self-assembly, as... Figure 4C As shown. Then, a portion of the dielectric region 250 (e.g., composed of SiO2) can be formed over the vias 212, 214, 216 and the reflective layer 202, as shown. Figure 4D As shown. Figure 4E As shown, chemical mechanical polishing (CMP) or other suitable removal techniques can be performed on dielectric region 250 until the top surface of dielectric region 250 is at the same level as the upper part of vias 212, 214, 216, as shown in the figure. Then, as... Figure 4F As shown, the reflective layer 120 can be formed above a flat surface. (As illustrated...) Figure 4G As shown, the layer stack can be etched to form a tapered structure as illustrated. Then, another portion forming the dielectric region 250 can be deposited or otherwise, such as... Figure 4HAs shown, the dielectric region 250 is then subjected to CMP such that the upper surface of the dielectric region 250 is at the same level as the top surface of the reflective layer 120, as shown. Figure 4I As shown, the dielectric region 250 is then subjected to CMP such that the upper surface of the dielectric region 250 is at the same level as the top surface of the reflective layer 120, as shown. Figure 2 As shown, the dielectric region 250 is then subjected to CMP such that the upper surface of the dielectric region 250 is at the same level as the top surface of the reflective layer 120, as shown.

[0042] Figure 5 is a flow diagram illustrating example operations 500 for signal processing in accordance with certain aspects of the present disclosure. The operations 500 can be performed, for example, by an electroacoustic device (e.g., a BAW resonator), such as the electroacoustic device 200.

[0043] The operations 500 can begin, at block 502, where the electroacoustic device receives a signal at a terminal (e.g., an electrode) of the electroacoustic device. At block 504, the electroacoustic device processes the signal. The electroacoustic device can include a substrate (e.g., the substrate 110), a bottom electrode layer (e.g., the electrode structure 106) disposed above the substrate, and an acoustic mirror stack. The acoustic mirror stack can include a first dielectric layer (e.g., the reflective layer 122) disposed above the bottom electrode layer and a first conductive layer (e.g., the reflective layer 120) disposed above the first dielectric layer. In certain aspects, the electroacoustic device can include a piezoelectric layer (e.g., the piezoelectric layer 104) disposed above the acoustic mirror stack and one or more first vias (e.g., the vias 212, 214, 216) disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and the first conductive layer.

[0044] In some aspects, the terminal of the electroacoustic device that receives the signal can be the bottom electrode layer. In some aspects, the electroacoustic device can include a top electrode layer (e.g., the electrode structure 102) disposed above the piezoelectric layer. In some cases, the terminal of the electroacoustic device that receives the signal can be the top electrode layer.

[0045] In some aspects, the acoustic mirror stack can include one or more second dielectric layers (e.g., the reflective layer 118) disposed above the bottom electrode layer, one or more second conductive layers (e.g., the reflective layer 116) each disposed above a respective second dielectric layer of the one or more second dielectric layers, and one or more second vias (e.g., the vias 206, 208, 210) disposed between the first conductive layer and a respective second conductive layer of the one or more second conductive layers. The one or more second vias can electrically couple the first conductive layer and the respective second conductive layer of the one or more second conductive layers. In some aspects, the piezoelectric layer can be in direct contact with an uppermost second conductive layer (e.g., the reflective layer 116) of the one or more second conductive layers. In some aspects, the piezoelectric layer can be in direct contact with the first conductive layer.

[0046] In certain aspects, the electroacoustic device can also include a second conductive layer (e.g., reflective layer 202) coupled between the bottom electrode layer and the first dielectric layer. The first conductive layer can include tungsten (W). In some aspects, the one or more first vias include aluminum (Al) or aluminum copper (AlCu), W, Mo, or any other suitable material. In certain aspects, the electroacoustic device can include a second dielectric layer (e.g., dielectric layer 260) between the substrate and the bottom electrode layer. In some implementations, the thickness of the bottom electrode layer can be greater than 100 nanometers.

[0047] Figure 6 is a block diagram of an example RF transceiver 600 in accordance with certain aspects of the present disclosure. In certain aspects, the electroacoustic devices described herein can be used in various circuits, such as RF transceivers, to function as electroacoustic filters or duplexers. The RF transceiver 600 includes at least one transmit (TX) path 602 (also referred to as a transmit chain) for transmitting signals via one or more antennas 606 and at least one receive (RX) path 604 (also referred to as a receive chain) for receiving signals via the antennas 606. When the TX path 602 and the RX path 604 share an antenna 606, the paths can connect with the antenna via an interface 608, which can include any of a variety of suitable RF devices, such as an electroacoustic filter 638 (e.g., electroacoustic filter circuit 300), a duplexer (which can include a BAW resonator), an antenna share, a multiplexer, etc.

[0048] The TX path 602 can receive an in-phase (I) or quadrature (Q) baseband analog signal from a digital-to-analog converter (DAC) 610, and can include a baseband filter (BBF) 612, a mixer 614, a driver amplifier (DA) 616, and a power amplifier (PA) 618. In certain aspects, the BBF 612, the mixer 614, and the DA 616 can be included in a semiconductor device, such as a radio frequency integrated circuit (RFIC), while the PA 618 can be external to the semiconductor device.

[0049] The BBF 612 filters the baseband signal received from the DAC 610, and the mixer 614 mixes the filtered baseband signal with a transmit local oscillator (LO) signal to convert the baseband signal of interest to a different frequency (e.g., upconvert from baseband to radio frequency). This frequency conversion process produces sum and difference frequencies between the LO frequency and the frequency of the baseband signal of interest. The sum and difference frequencies are referred to as the beat frequencies. The beat frequencies are typically in the RF range, such that the signal output by the mixer 614 is typically an RF signal, which can be amplified by the DA 616 and / or the PA 618 before being transmitted by the antenna 606. In certain cases, the BBF 612 can be implemented using an electroacoustic filter (e.g., electroacoustic filter circuit 300) having a BAW resonator.

[0050] The RX path 604 may include a low-noise amplifier (LNA) 624, a filter 626, a mixer 628, and a baseband filter (BBF) 630. The LNA 624, filter 626, mixer 628, and BBF 630 may be included in an RFIC, which may or may not be the same RFIC that includes the TX path component. The RF signal received via antenna 606 may be amplified by the LNA 624 and filtered by the filter 626, and the mixer 628 mixes the amplified RF signal with a received local oscillator (LO) signal to convert the RF signal of interest to a different baseband frequency (e.g., down-conversion). The baseband signal output from the mixer 628 may be filtered by the BBF 630 before being converted into digital I or Q signals by an analog-to-digital converter (ADC) 632 for digital signal processing. In some cases, the filter 626 and / or the BBF 630 may be implemented using an electroacoustic filter with a BAW resonator (e.g., electroacoustic filter circuit 300).

[0051] While it is desirable for the LO output to remain frequency-stable, tuning to different frequencies indicates the use of a frequency converter oscillator, which may involve a trade-off between stability and tunability. Modern systems can use frequency synthesizers with voltage-controlled oscillators (VCOs) to generate stable, tunable LOs with specific tuning ranges. Therefore, the transmit LO can be generated by the TX frequency synthesizer 620, which can be buffered or amplified by the amplifier 622 before being mixed with the baseband signal in the mixer 614. Similarly, the receive LO can be generated by the RX frequency synthesizer 634, which can be buffered or amplified by the amplifier 636 before being mixed with the RF signal in the mixer 628.

[0052] Figure 7 This is a schematic diagram of an environment 700 including a wireless communication device 702, which has features such as Figure 6 The RF transceiver 600 and other wireless transceivers 722 are used. In environment 700, wireless communication device 702 communicates with base station 704 via wireless link 706. As shown, wireless communication device 702 is depicted as a smartphone. However, electronic wireless communication device 702 can be implemented as any suitable computing or other electronic device, such as cellular base station, broadband router, access point, cellular or mobile phone, gaming device, navigation device, media device, laptop computer, desktop computer, tablet computer, server computer, network-connected storage (NAS) device, smart device, vehicle-based communication system, Internet of Things (IoT) device, sensor or security device, asset tracker, etc.

[0053] The base station 704 communicates with the wireless communication device 702 via a wireless link 706, which can be implemented as any suitable type of wireless link. Although depicted as a base station tower of a cellular radio network, the base station 704 can represent or be implemented as another device, such as a satellite, a terrestrial broadcast tower, an access point, a peer-to-peer device, a mesh network node, a fiber optic line, another electronic device generally as described above, etc. Thus, the wireless communication device 702 can communicate with the base station 704 or another device via a wired connection, a wireless connection, or a combination thereof. The wireless link 706 can include a downlink of data or control information communicated from the base station 704 to the wireless communication device 702, and an uplink of other data or control signals communicated from the wireless communication device 704 to the base station 704. The wireless link 706 can be implemented using any suitable communication protocol or standard, such as Third Generation Partnership Project Long-Term Evolution (3GPP LTE), 3GPP New Radio Fifth Generation (NR 5G), IEEE 802.11 (WiFi), IEEE 802.16 (WiMAX), Bluetooth TM etc.

[0054] The wireless communication device 702 includes a processor 708 and a memory 710. The memory 710 can be or form part of a computer-readable storage medium. The processor 708 can include any type of processor, such as an application processor or a multi-core processor, configured to execute processor-executable instructions (e.g., code) stored by the memory 710. The memory 710 can include any suitable type of data storage media, such as volatile memory (e.g., random access memory (RAM)), non-volatile memory (e.g., flash memory), optical media, magnetic media (e.g., disk or tape), etc. In the context of the present disclosure, the memory 710 is implemented to store instructions 712, data 714, and other information of the wireless communication device 702, and thus the memory 710 does not include transitory propagating signals or carrier waves when configured as a computer-readable storage medium or part thereof. That is, the memory 710 can include non-transitory computer-readable media (e.g., tangible media).

[0055] The wireless communication device 702 can also include an input / output port 716. The I / O port 716 enables data exchange or interaction with other devices, networks, or users, or exchange or interaction of data between components of the device.

[0056] The wireless communication device 702 can also include a signal processor (SP) 718 (e.g., such as a digital signal processor (DSP)). The signal processor 718 is similar in functionality to the processor 708, and the signal processor 718 is capable of executing instructions and / or processing information in conjunction with the memory 710.

[0057] For communication purposes, the wireless communication device 702 also includes a modem 720, a wireless transceiver 722, and an antenna (not shown). The wireless transceiver 722 provides connectivity to respective networks and other wireless communication devices connected thereto using radio frequency (RF) wireless signals, and can include an RF transceiver 600. The wireless transceiver 722 can 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, a wireless wide area network (WW AN), a navigation network (e.g., the Global Positioning System (GPS) in North America or another Global Navigation Satellite System (GNSS)), and / or a wireless personal area network (WPAN). Figure 6

[0058] Figure 8 is a flow diagram illustrating example operations 800 for manufacturing an electroacoustic device, in accordance with certain aspects of the present disclosure. The operations 800 can be performed, for example, by a manufacturing device.

[0059] The operations 800 can begin, at block 802, with a manufacturing facility forming a bottom electrode layer (e.g., the electrode structure 106) over a substrate. At block 804, the manufacturing facility forms an acoustic mirror stack including a first dielectric layer (e.g., the reflective layer 122) disposed over the bottom electrode layer and a second conductive layer (e.g., the reflective layer 120) disposed over the first dielectric layer. At block 806, the manufacturing facility forms one or more vias (e.g., the vias 212, 214, 216) that electrically couple the bottom electrode layer and the first conductive layer, and at block 808, forms a piezoelectric layer (e.g., the piezoelectric layer 104) over the acoustic mirror stack.

[0060] Example Aspects

[0061] Aspect 1. An electroacoustic device, comprising:

[0062] a substrate;

[0063] a bottom electrode layer disposed over the substrate;

[0064] an acoustic mirror stack having:

[0065] a first dielectric layer disposed over the bottom electrode layer; and

[0066] a first conductive layer disposed over the first dielectric layer;

[0067] a piezoelectric layer disposed over the acoustic mirror stack; and

[0068] ​one or more first vias disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and first conductive layer.

[0069] Aspect 2. The electro-acoustic device of Aspect 1, further comprising a top electrode layer disposed above the piezoelectric layer.

[0070] Aspect 3. The electro-acoustic device of any one of Aspects 1-2, wherein the acoustic mirror stack further comprises:

[0071] one or more second dielectric layers disposed above the bottom electrode layer;

[0072] one or more second conductive layers each disposed above a respective second dielectric layer of the one or more second dielectric layers; and

[0073] one or more second vias disposed between the first conductive layer and a respective second conductive layer of the one or more second conductive layers, the one or more second vias electrically coupling the first conductive layer and the respective second conductive layer of the one or more second conductive layers.

[0074] Aspect 4. The electro-acoustic device of Aspect 3, wherein the piezoelectric layer is in direct contact with an uppermost conductive layer of the one or more second conductive layers.

[0075] Aspect 5. The electro-acoustic device of any one of Aspects 1-2, wherein the piezoelectric layer is in direct contact with the first conductive layer.

[0076] Aspect 6. The electro-acoustic device of any one of Aspects 1-2 and 5, further comprising a third conductive layer coupled between the bottom electrode layer and the first dielectric layer.

[0077] Aspect 7. The electro-acoustic device of any one of Aspects 1-6, wherein the first dielectric layer comprises silicon dioxide (SiO2).

[0078] Aspect 8. The electro-acoustic device of any one of Aspects 1-7, wherein the first conductive layer comprises tungsten (W).

[0079] Aspect 9. The electro-acoustic device of any one of Aspects 1-8, wherein the one or more first vias comprise tungsten (W) or molybdenum (Mo).

[0080] Aspect 10. The electro-acoustic device of any one of Aspects 1-2 and 5-9, further comprising a third dielectric layer between the substrate and the bottom electrode layer.

[0081] Aspect 11. The electroacoustic device of any one of aspects 1-10, wherein the electroacoustic device is configured as a bulk acoustic wave (BAW) resonator.

[0082] Aspect 12. A radio frequency (RF) filter comprising the electroacoustic device of any one of aspects 1-11.

[0083] Aspect 13. The electroacoustic device of any one of aspects 1-12, wherein a thickness of the bottom electrode layer is greater than 100 nanometers.

[0084] Aspect 14. A method for signal processing, comprising:

[0085] receiving a signal at a terminal of an electroacoustic device; and

[0086] processing the signal via the electroacoustic device, wherein the electroacoustic device comprises:

[0087] a substrate;

[0088] a bottom electrode layer disposed above the substrate;

[0089] an acoustic mirror stack having:

[0090] a first dielectric layer disposed above the bottom electrode layer; and

[0091] a first conductive layer disposed above the first dielectric layer;

[0092] a piezoelectric layer disposed above the acoustic mirror stack; and

[0093] one or more first vias disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and first conductive layer.

[0094] Aspect 15. The method of aspect 14, wherein the terminal of the electroacoustic device comprises the bottom electrode layer.

[0095] Aspect 16. The method of aspect 14, wherein the electroacoustic device further comprises a top electrode layer disposed above the piezoelectric layer, the terminal of the electroacoustic device comprising the top electrode layer.

[0096] Aspect 17. The method of any one of aspects 14-16, wherein the acoustic mirror stack further comprises:

[0097] one or more second dielectric layers disposed above the bottom electrode layer;

[0098] one or more second conductive layers each disposed above a respective second dielectric layer of the one or more second dielectric layers; and

[0099] one or more second vias disposed between the first conductive layer and a respective second conductive layer of the one or more second conductive layers, the one or more second vias electrically coupling the first conductive layer and the respective second conductive layer of the one or more second conductive layers.

[0100] Aspect 18. The method of Aspect 17, wherein the piezoelectric layer is in direct contact with an uppermost conductive layer of the one or more second conductive layers.

[0101] Aspect 19. The method of any one of Aspects 14-16, wherein the piezoelectric layer is in direct contact with the first conductive layer.

[0102] Aspect 20. The method of any one of Aspects 14-16 and 19, wherein the electroacoustic device further comprises a third conductive layer coupled between the bottom electrode layer and the first dielectric layer.

[0103] Aspect 21. The method of any one of Aspects 14-20, wherein the first dielectric layer comprises silicon dioxide (SiO2).

[0104] Aspect 22. The method of any one of Aspects 14-21, wherein the first conductive layer comprises tungsten (W).

[0105] Aspect 23. The method of any one of Aspects 14-22, wherein the one or more first vias comprise tungsten (W) or molybdenum (Mo).

[0106] Aspect 24. The method of any one of Aspects 14-16 and 19-23, wherein the electroacoustic device further comprises a third dielectric layer between the substrate and the bottom electrode layer.

[0107] Aspect 25. The method of any one of Aspects 14-24, wherein the electroacoustic device is configured as a bulk acoustic wave (BAW) resonator.

[0108] Aspect 26. The method of any one of Aspects 14-25, wherein a thickness of the bottom electrode layer is greater than 100 nanometers.

[0109] Aspect 27. A method of fabricating an electroacoustic device, comprising:

[0110] forming a bottom electrode layer over a substrate;

[0111] forming an acoustic mirror stack, the acoustic mirror stack comprising:

[0112] a first dielectric layer disposed over the bottom electrode layer; and

[0113] a first conductive layer disposed over the first dielectric layer;

[0114] forming one or more vias that electrically couple the bottom electrode layer and the first conductive layer; and

[0115] forming a piezoelectric layer over the acoustic mirror stack.

[0116] The various operations of methods described above can be performed by any suitable means capable of performing the corresponding functions. The means can include various hardware and / or software component(s) and / or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations can have corresponding counterpart means-plus-function components.

[0117] The following description provides examples of electroacoustic devices for various filtering applications and does not limit the scope, applicability, or examples set forth in the claims. Changes can be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples can omit, substitute, or add various procedures or components as appropriate. For instance, the methods described can be performed in an order different than described, and / or various steps can be added, omitted, or combined. Also, features described with respect to some examples can be combined in some other examples. For example, an apparatus or a method can be implemented using any number of the aspects set forth herein. Also, the scope of the disclosure is intended to cover apparatuses or methods that are implemented using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure described herein. It is understood that any aspect of the disclosure disclosed herein can be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

[0118] The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and / or actions can be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order is specified, the order or sequence of any step or action can be modified without departing from the scope of the claims.

[0119] As used herein, the term “at least one” means any combination of the items, including single members. For example, “at least one of a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination of multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

[0120] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited in the claim as a means plus function.

[0121] Various operations can be performed by any suitable means capable of performing the corresponding function. The means can include various hardware components. Generally, where operations are shown in the figures, those operations can have corresponding counterpart means-plus-function components with similar numbering.

[0122] It is to be understood that the claims are not limited to the precise arrangements and components described above. Various modifications, changes, and variations can be made to the arrangements, operation, and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. An electro-acoustic device, comprising: a substrate; a bottom electrode layer disposed above the substrate; an acoustic mirror stack having: a first dielectric layer disposed above the bottom electrode layer; and a first conductive layer disposed above the first dielectric layer; a piezoelectric layer disposed above the acoustic mirror stack; and one or more first vias disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and the first conductive layer.

2. The electro-acoustic device of claim 1, further comprising a top electrode layer disposed above the piezoelectric layer.

3. The electro-acoustic device of claim 1, wherein the acoustic mirror stack further comprises: one or more second dielectric layers disposed above the bottom electrode layer; one or more second conductive layers each disposed above a respective second dielectric layer of the one or more second dielectric layers; and one or more second vias disposed between the first conductive layer and a respective second conductive layer of the one or more second conductive layers, the one or more second vias electrically coupling the first conductive layer and the respective second conductive layer of the one or more second conductive layers.

4. The electro-acoustic device of claim 3, wherein the piezoelectric layer is in direct contact with an uppermost conductive layer of the one or more second conductive layers.

5. The electro-acoustic device of claim 1, wherein the piezoelectric layer is in direct contact with the first conductive layer.

6. The electro-acoustic device of claim 1, further comprising a second conductive layer coupled between the bottom electrode layer and the first dielectric layer.

7. The electro-acoustic device of claim 1, wherein the first dielectric layer comprises silicon dioxide (SiO2).

8. The electro-acoustic device of claim 1, wherein the first conductive layer comprises tungsten (W).

9. The electro-acoustic device of claim 1, wherein the one or more first vias comprise tungsten (W) or molybdenum (Mo).

10. The electro-acoustic device of claim 1, further comprising a second dielectric layer between the substrate and the bottom electrode layer.

11. The electro-acoustic device of claim 1, wherein the electro-acoustic device is configured as a bulk acoustic wave (BAW) resonator.

12. The electro-acoustic device of claim 1, wherein a thickness of the bottom electrode layer is greater than 100 nanometers.

13. A radio frequency (RF) filter comprising the electro-acoustic device of claim 1.

14. A method for signal processing, comprising: receiving a signal at a terminal of an electro-acoustic device; and processing the signal via the electro-acoustic device, wherein the electro-acoustic device comprises: a substrate; a bottom electrode layer disposed above the substrate; an acoustic mirror stack having: a first dielectric layer disposed above the bottom electrode layer; and a first conductive layer disposed above the first dielectric layer; a piezoelectric layer disposed above the acoustic mirror stack; and ​ ​ ​ ​ one or more first vias disposed between the bottom electrode layer and the first conductive layer, the one or more first vias electrically coupling the bottom electrode layer and first conductive layer.

15. The method of claim 14, wherein the terminal of the electro-acoustic device comprises the bottom electrode layer.

16. The method of claim 14, wherein the electro-acoustic device further comprises a top electrode layer disposed above the piezoelectric layer, the terminal of the electro-acoustic device comprising the top electrode layer.

17. The method of claim 14, wherein the acoustic mirror stack further comprises: one or more second dielectric layers disposed above the bottom electrode layer; one or more second conductive layers each disposed above a respective second dielectric layer of the one or more second dielectric layers; and one or more second vias disposed between the first conductive layer and a respective second conductive layer of the one or more second conductive layers, the one or more second vias electrically coupling the first conductive layer and the respective second conductive layer of the one or more second conductive layers.

18. The method of claim 17, wherein the piezoelectric layer is in direct contact with an uppermost conductive layer of the one or more second conductive layers.

19. The method of claim 14, wherein the piezoelectric layer is in direct contact with the first conductive layer.

20. The method of claim 14, wherein the electro-acoustic device further comprises a second conductive layer coupled between the bottom electrode layer and the first dielectric layer.

21. The method of claim 14, wherein the first dielectric layer comprises silicon dioxide (SiO2).

22. The method of claim 14, wherein the first conductive layer comprises tungsten (W).

23. The method of claim 14, wherein the one or more first vias comprise tungsten (W) or molybdenum (Mo).

24. The method of claim 14, wherein the electro-acoustic device further comprises a second dielectric layer between the substrate and the bottom electrode layer.

25. The method of claim 14, wherein the electro-acoustic device is configured as a bulk acoustic wave (BAW) resonator.

26. The method of claim 14, wherein a thickness of the bottom electrode layer is greater than 100 nanometers.

27. A method of manufacturing an electro-acoustic device, comprising: forming a bottom electrode layer above a substrate; forming an acoustic mirror stack, the acoustic mirror stack comprising: a first dielectric layer disposed above the bottom electrode layer; and a first conductive layer disposed above the first dielectric layer; forming one or more vias, the one or more vias electrically coupling the bottom electrode layer and the first conductive layer; and forming a piezoelectric layer above the acoustic mirror stack.

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