Piezoelectric audio device

Abstract

The invention relates to a piezoelectric audio device. In one example, an audio device includes a substrate, a first piezoelectric fin (102A), a second piezoelectric fin (102B), a transmit circuit (130A, 130B), a first receive circuit (140A), a switch circuit (120B), and a second receive circuit (140B). The substrate has an opening (118). The first piezoelectric fin has a first end portion on the substrate and extending over the opening, the first piezoelectric fin having a first terminal (170A) and a second terminal (172A). A second piezoelectric fin has a second end extending over the opening on the substrate, the second piezoelectric fin being spaced apart from the first piezoelectric fin, the second piezoelectric fin having a third terminal (170B) and a fourth terminal (172B). The transmission circuit has a driver output (132A-134A). The first receive circuit has a first receiver input (142A-144A). A switching circuit is coupled to the driver output and the first receiver input, and a first terminal and a second terminal. The second receive circuit has a second receiver input (142B-144B) coupled to the third terminal and the fourth terminal.

Description

[0001] Related Applications

[0002] This application is related to U.S. patent application No. 18 / 240,676, entitled “Piezoelectric audio device” and filed on August 31, 2023, with agent file number T103884US01, the entire contents of which are incorporated herein by reference. Background Art

[0003] Piezoelectric transducers can convert mechanical energy (e.g., vibration) to electrical energy using the piezoelectric effect. Audio devices such as speakers can include a piezoelectric film that can vibrate in response to an audio signal to generate an audible sound wave / acoustic signal. Audio devices such as microphones can also include a piezoelectric flap that includes electrodes that can vibrate in response to external sound waves and generate an electrical signal representing the sound wave. The electrical signal can then be further processed, for example, to generate an audio signal, or to extract other information.

[0004] The piezoelectric fins of an audio device may have a frequency response that peaks at a specific resonant frequency. The frequency response determines how the piezoelectric fins convert between sound waves and audio signals across different frequencies. The resonant frequency may be based on a specific frequency of interest to improve the separation of the desired audio signal and noise. At least at the beginning, by selecting the correct material and size, the overall frequency response of the piezoelectric fins, including their resonant frequency, may be tuned. However, the resonant frequency may be affected by the residual stress in the layers that constitute the piezoelectric transducer. Due to initial processing and during the working life of the piezoelectric transducer due to mechanical fatigue and / or by the introduction of foreign matter (e.g., particles or moisture), such stress changes may exist across a given piezoelectric fin. All of these may cause the actual frequency response of the piezoelectric fins to shift from the design / target frequency response, which may degrade the fidelity of the audio device in converting between sound waves and audio signals. Summary of the invention

[0005] In one example, an audio device includes a substrate, a first piezoelectric fin, a second piezoelectric fin, a transmitting circuit, a first receiving circuit, a switching circuit, and a second receiving circuit. The substrate has an opening. The first piezoelectric fin has a first end extending on the substrate and above a first portion of the opening, and the first piezoelectric fin has a first terminal and a second terminal. The second piezoelectric fin has a second end extending on the substrate and above a second portion of the opening, the second piezoelectric fin is spaced apart from the first piezoelectric fin, and the second piezoelectric fin has a third terminal and a fourth terminal. The transmitting circuit has a driver output. The first receiving circuit has a first receiver input. The switching circuit has a first switch terminal and a second switch terminal, the first switch terminal is coupled to the driver output and the first receiver input, and the second switch terminal is coupled to the first terminal and the second terminal. The second receiving circuit has a second receiver input coupled to the third terminal and the fourth terminal.

[0006] In one example, a method includes driving a first piezoelectric flap of an audio device with a first electrical signal to generate an acoustic signal. The method further includes receiving a second electrical signal from a second piezoelectric flap of the audio device in response to the acoustic signal. The method also includes determining a characteristic of the audio device based on the second electrical signal, and performing an action based on the characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A and Figure 1B is a schematic diagram of an example piezoelectric audio device.

[0008] Figure 2 is a schematic diagram illustrating an example operation of the audio device of FIG. 1 in a microphone mode.

[0009] Figure 3 is a schematic diagram illustrating an example operation of the piezoelectric audio device of FIG. 1 in a self-test mode.

[0010] Figure 4 is a schematic diagram showing another example of the piezoelectric audio device of FIG. 1 .

[0011] Figure 5 Figure 1 and Figure 4 Schematic diagram of example subcomponents of a piezoelectric audio device.

[0012] Figure 6 Figure 1 and Figure 4 A graph of an example frequency spectrum of a piezoelectric audio device providing an electrical signal.

[0013] Figure 7 is a flow chart of an example method of operating a piezoelectric audio device.

[0014] Fig. 8A and Figure 8Bis a schematic diagram showing various views of an example piezoelectric cantilever system.

[0015] Fig. 9A and Fig. 9B is a schematic diagram showing various views of an example piezoelectric bimorph that can be used as Fig. 8A and Figure 8B Parts of the piezoelectric cantilever system.

[0016] Fig. 10A It shows the manufacturing Fig. 9A and Fig. 9B Flow chart of an example piezoelectric bimorph method.

[0017] Fig. 10B , Fig. 10C , Fig. 10D , Fig.10E , Fig.10F and Figure 10G It shows the manufacturing Fig. 9A and Fig. 9B Schematic diagram of the various stages of an example piezoelectric bimorph.

[0018] Fig.11A and Fig. 11B is a schematic diagram showing various views of an example piezoelectric bimorph that can be used as Fig. 9A and Fig. 9B Parts of the piezoelectric cantilever system.

[0019] Fig. 12A It shows the manufacturing Fig.11A and Fig. 11B Flow chart of an example piezoelectric bimorph method.

[0020] Fig. 12B , Fig. 12C , Fig.12D , Fig.12E , Fig.12F , Figure 12G , Fig.12H and Fig.12I It shows the manufacturing Fig.11A and Fig. 11B Schematic diagram of the various stages of an example piezoelectric bimorph.

[0021] Fig.13A and Fig. 13B is a schematic diagram showing various views of another example piezoelectric bimorph that can be used as Fig. 9A and Fig. 9B Parts of the piezoelectric cantilever system.

[0022] Fig.14A and Fig. 14Bis a schematic diagram showing various views of another example piezoelectric bimorph that can be used as Fig. 9A and Fig. 9B Parts of the piezoelectric cantilever system.

[0023] Fig.15A It shows the manufacturing Figure 13A-Figure 14B Flow chart of an example piezoelectric bimorph method.

[0024] Fig. 15B , Fig. 15C , Fig.15D and Fig.15E It is shown in Fig.15A Manufacturing Figure 13A-Figure 14B Schematic diagram of the various stages of an example piezoelectric bimorph.

[0025] The same reference numerals or other reference numerals are used in the drawings to denote the same or similar (functionally and / or structural) features. The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0026] Figure 1A An example audio device 100 is shown. In some examples, the audio device 100 can be configured as a microphone. In some examples, the audio device 100 can be configured as a speaker. The audio device 100 can be a packaged device including a piezoelectric cantilever system 110 and an integrated circuit 150 on a substrate 190. The substrate 190 can be a package substrate, a printed circuit board (PCB), etc.

[0027] The piezoelectric cantilever system 110 includes a plurality of piezoelectric tabs, such as 102A and 102B. One end of each membrane is coupled to a structure 114 (e.g., a semiconductor structure) having an opening 116, and the other end of each tab can move up / down as a cantilever / tab above the opening 116. The tabs are separated by gaps / slits 118, which allow each tab to move independently relative to each other in certain operations. As described below, each piezoelectric tab of the piezoelectric cantilever system 110 is individually addressable / controllable, wherein each piezoelectric tab can be independently operated as a sensor (e.g., as part of a microphone to detect sound waves and convert them into electrical signals) or as an actuator (e.g., as a speaker to generate sound waves or otherwise move the tab).

[0028] In some examples, the piezoelectric cantilever system 110 can be a microelectromechanical system (MEMS) or a nanoelectromechanical system (NEMS), in which the fins are manufactured in micrometer or nanometer dimensions, respectively. Certain MEMS or NEMS technologies can provide several benefits, such as batch manufacturing that can reduce manufacturing costs, small feature sizes, high resonant frequencies, and improved impedance matching.

[0029] The integrated circuit 150 is communicatively coupled to the piezoelectric cantilever system 110 via interconnects (e.g., bond wires 151) and may be encapsulated in epoxy 154. The integrated circuit 150 may include a control and processing circuit (CPC) 152 and a set of switches, both of which will be Figure 1B , to operate each individually controllable piezoelectric bimorph flap to perform the aforementioned self-test, self-calibration, and self-cleaning operations. In some examples, the piezoelectric cantilever system 110 and the integrated circuit 150 are on separate dies, such as Figure 1A In some examples, the piezoelectric cantilever system 110 and the integrated circuit 150 are on the same die.

[0030] Substrate 190 also includes opening 119, which connects opening 116 and exposes the piezoelectric fin to the outside of audio device 100. Openings 116 and 120 can define a front volume space (or audio port). In the case where CPC 152 operates the piezoelectric fin as part of a microphone, the piezoelectric fin can detect sound waves propagating from the outside of audio device 100 via the front volume space defined by openings 120 and 116, and generate electrical signals in response to the detection of sound waves. In addition, as described below, in a self-test operation, CPC 152 can drive one or more piezoelectric fins (e.g., sheet 102A) of piezoelectric cantilever system 110 as actuators to generate internal sound waves, and operate another one or more piezoelectric fins (e.g., fin 102B) of piezoelectric cantilever system 110 as sensors. The internal sound waves can propagate through the front volume space / audio port and reach fin 102B, and fin 102B can generate electrical signals in response to detecting the internal sound waves. From the electrical signal, CPC 152 may extract various properties of the piezoelectric foil (eg, frequency response, resonant frequency, etc.) as a result of a self-test operation.

[0031] The audio device 100 also includes a housing 191 mounted on the substrate 190. The housing 191 can cover the piezoelectric cantilever system 110, the integrated circuit 150, the bonding wires 151, and the epoxy material 154. The housing 191 can be made of any suitable material, such as metal, plastic, etc., to protect the piezoelectric cantilever system 110 and the integrated circuit 150 from noise and mechanical stress. The housing 191 can also define a rear volume space 192 in which the piezoelectric fin of the piezoelectric cantilever system 110 can move (e.g., vibrate). The rear volume space 192 can be filled with air. The slit / gap 118 allows air to flow between the rear volume space 192 and the front volume space (defined by the openings 116 and 120) to equalize the air pressure on both sides of the piezoelectric fin, thereby preventing additional stress, which otherwise may damage or reduce the sensitivity of the piezoelectric fin when operating as a microphone. The slit / gap 118 is also narrow (eg, 1 micrometer (um)) to prevent sound waves from reaching the back volume 192 and may set the lower cutoff frequency of the microphone.

[0032] As described below, CPC 152 can also perform an equalization operation and / or a self-cleaning operation based on the result of the self-test operation. For example, CPC 152 can determine the frequency response of piezoelectric cantilever system 110 based on the self-test operation, and determine a set of equalization coefficients based on the frequency response. When the piezoelectric cantilever system 110 is operated as a microphone, CPC 152 can use the set of equalization coefficients to perform an equalization operation on the electrical signal received from the piezoelectric cantilever system 110 to obtain the desired / target frequency response of the audio device 100 (e.g., a flat frequency response across a specific frequency range, a peak response at a specific resonant frequency, etc.). As another example, according to the self-test operation, CPC 152 can detect foreign matter (e.g., moisture) on the piezoelectric fin, in the rear volume space 192, in the front volume space, etc. In response to the detection of foreign matter, CPC 152 can transmit an electrical drive signal to vibrate the piezoelectric fin to remove the foreign matter. The CPC 152 may also determine the resonant frequency of the piezoelectric cantilever system 110 from self-testing and drive the piezoelectric foil at the resonant frequency to maximize (or at least increase) the driving and cleaning efficiency.

[0033] In some examples, the audio device 100 may also include a heating element 194 (e.g., a resistor) to support self-cleaning operation. The heating element 194 may be activated by the CPC 152 to radiate heat to help remove moisture from the audio device 100 (e.g., by evaporation). Figure 1AAs shown, a heating element 194 can be located within the rear volume 192 (e.g., attached to the housing 191) to heat moisture in the rear volume and / or on the piezoelectric fins, and the moisture can evaporate out of the openings 116 and 119 via the gap / slit 118. The heating element 194 can also be located on or near the IC 150, the package substrate 190, and / or the piezoelectric cantilever system 110 to interface with the rear volume 192. As another example, the heater 194 can be located near the openings 116 and / or 119 to evaporate moisture present in the front volume.

[0034] Figure 1B 1 is a block diagram showing the internal components of the piezoelectric cantilever system 110 and the integrated circuit 150. Figure 1B As shown, the integrated circuit 150 includes the piezoelectric cantilever system 110 , one or more switch networks 120A- 120B, one or more transmit circuits 130A- 130B, one or more receive circuits 140A- 140B, and the CPC 152 .

[0035] refer to Figure 1B , the piezoelectric cantilever system 110 includes two piezoelectric fins 102A-102B. Each piezoelectric fin may be a piezoelectric bimorph fin having a multilayer structure. Each bimorph fin has a top electrode, a middle electrode, a bottom electrode, a first piezoelectric layer between the top electrode and the middle electrode, and a second piezoelectric layer between the middle electrode and the bottom electrode. Although the illustrated portion of the piezoelectric system 110 shows two bimorph fins 102A and 102B, the piezoelectric cantilever system 110 may include any suitable number of fins 102. For example, Figure 4 A perspective view of a piezoelectric microphone 410 is shown having four fins 402A, 402B, 402C, and 402D.

[0036] The bimorph fins 102A and 102B are formed on a structure 114, which may include multiple layers forming a stack. For example, the structure 114 may include an oxide layer 192 and a substrate 194 (e.g., a silicon substrate). As described above, the structure 114 includes an opening 106 formed therethrough, which allows sound waves to pass into or out of the fins 102A and 102B through the opening 106. The bimorph fins 102A and 102B are both cantilevered, so that the corresponding fixed portion is on the structure 114, and the corresponding movable portion extends over the corresponding portion of the opening 106. As described above, the bimorph fins 102A and 102B separate the rear volume space 192 of the audio device 100 from the opening 106.

[0037] like Figure 1BAs shown, the bimorph fin 102A has a top electrode 160A, an intermediate electrode 162A, and a bottom electrode 164A. At least a portion of the intermediate electrode 162A is located between the top electrode 160A and the bottom electrode 164A. The bimorph fin 102A also has at least two piezoelectric layers 180A and 182A. The piezoelectric layer 180A has at least a portion between the top electrode 160A and the intermediate electrode 162A. The piezoelectric layer 182A has at least a portion between the intermediate electrode 162A and the bottom electrode 164A. The top electrode 160A and the bottom electrode 164A are coupled to a terminal 170A. The intermediate electrode 162A is coupled to another terminal 172A.

[0038] In addition, the bimorph fin 102B has a top electrode 160B, an intermediate electrode 162B, and a bottom electrode 164B. At least a portion of the intermediate electrode 162B is located between the top electrode 160B and the bottom electrode 164B. The bimorph fin 102B also has at least two piezoelectric layers 180B and 182B. The piezoelectric layer 180B has at least a portion between the top electrode 160B and the intermediate electrode 162B. The piezoelectric layer 182B has at least a portion between the intermediate electrode 162B and the bottom electrode 164B. The top electrode 160B and the bottom electrode 164B are coupled to a terminal 172B. The intermediate electrode 162B is coupled to another terminal 170B.

[0039] The electrodes 160A-160B, 162A-162B, and 164A-164B can each be made of one or more layers of any suitable (one or more) conductive materials. The piezoelectric layers 180A-180B and 182A-182B and 184A-184B can each be formed of any suitable (one or more) piezoelectric materials. In some examples, the electrodes 160A-164B and the piezoelectric layers 180A-184B can all be formed using (one or more) materials compatible with certain CMOS processes. For example, molybdenum (Mo or "Molybdenum") can be used to form the electrodes 160A-160B, 162A-162B, and 164A-164B, and aluminum nitride ("AlN") can be used to form the piezoelectric layers 180A-180B and 182A-182B and 184A-184B. However, any suitable bimorph material(s) may be used to form the electrodes 160A-160B, 162A-162B, and 164A-164B and the piezoelectric layers 180A-180B, 182A-182B, and 184A-184B.

[0040] Terminals 170A, 172A, 170B, and 172B may include any suitable electrical connector configured to pass electrical current. Figure 1BAs shown, terminals 170A and 170B may be used to electrically couple bimorph piezoelectric tab 102A to switch network 120A. Terminals 170B and 172B may be used to electrically couple bimorph piezoelectric tab 102B to switch circuit 120B.

[0041] Switching circuits 120A and 120B may include any suitable electrical component(s) configured to disconnect or connect conductive paths interconnecting CPC 152 with bimorph tabs 102A and 102B, respectively. For example, switching circuit 120A may be configured to disconnect or connect conductive paths to respective terminals 170A and 172A; and switching circuit 120B may be configured to disconnect or connect conductive paths to respective terminals 170B and 172B. Switching circuit 120A may have input terminals coupled to driver outputs 132A-134A of transmitting circuit 130A, and may further have output terminals coupled to receiver inputs 142A-144A of receiving circuit 140A. Switching circuit 120B may similarly have input terminals coupled to driver outputs 132B-134B of transmitting circuit 130B, and may further have output terminals coupled to receiver inputs 142B-144B of receiving circuit 140B.

[0042] Transmit circuits 130A and 103B may include circuitry that receives electrical signals (e.g., audio signals, self-cleaning signals, etc.) from CPC 152 at their inputs and transmits corresponding electrical signals to bimorph flaps 102A and 102B via switch circuits 120A and 120B, respectively, to generate sound waves and / or vibrate the bimorph flaps. Each of transmit circuits 130A and 130B may include an audio driver circuit. Transmit circuit 130A has a plurality of driver outputs 132A- and 134A coupled to corresponding inputs of switch circuit 120A. Transmit circuit 130B has a plurality of driver outputs 132B-134B coupled to corresponding inputs of switch circuit 120B. In operation, CPC 152 may provide a signal (e.g., an audio signal, a self-cleaning signal) to transmit circuit 130A or 130B, which converts the signal into an electrical drive signal having one or more frequencies to bimorph flaps 102A and / or 102B, respectively. Transmit circuit 130A may provide an electrical drive signal having a potential difference across driver output terminals 132A-134A via switch circuit 120A to generate an alternating electric field across bimorph flap 102A, which causes bimorph flap 102A to vibrate. Additionally, transmit circuit 130B may provide an electrical drive signal having a potential difference across driver output terminals 132B-134B via switch circuit 120B to generate an alternating electric field across bimorph flap 102B, which causes bimorph flap 102B to vibrate.

[0043] The receiving circuit 140A may include circuitry that receives electrical signals at the receiver inputs 142A and 144A and provides corresponding electrical signals to the CPC 152, the electrical signals representing the electric field between the electrodes 160A / 164A and 162A, which reflects the stress in the bimorph piezoelectric foil 102A caused by the acoustic wave. For example, the bimorph piezoelectric foil 102A may be configured to vibrate in response to the acoustic wave, thereby causing stress that is converted into an electrical signal, which is provided to the receiving circuit 140A via the inputs 142A and 144A. The receiving circuit 140A may perform a conversion operation on the received electrical signal. For example, the receiving circuit 140A may perform an analog-to-digital conversion, which involves receiving an analog electrical signal at the receiver inputs 142A and 144A and converting the received analog electrical signal into a digital electrical signal. The converted digital electrical signal may then be provided to the CPC 152. Alternatively, the receiving circuit 140A may provide an analog signal to the CPC 152, which may then convert the analog signal into a digital signal using an internal analog-to-digital converter (as described herein with reference to FIG. Figure 4 described above).

[0044] The receiving circuit 140B may include circuitry that receives electrical signals at the receiver inputs 142B and 144B and provides corresponding electrical signals to the CPC 152, the electrical signals representing the electric field between the electrodes 160B / 164B and 162B, which reflects the stress in the bimorph flap 102B caused by the sound waves. For example, the bimorph flap 102B may be configured to vibrate in response to the sound waves, thereby causing stress that is converted into an electrical signal, which is provided to the receiving circuit 140B via the input 142B or 144B. The receiving circuit 140B may perform a conversion operation on the received electrical signal. For example, the receiving circuit 140B may perform an analog-to-digital conversion, which involves receiving an analog electrical signal at the receiver inputs 142B and 144B and converting the received analog electrical signal into a digital electrical signal. The converted digital electrical signal may then be provided to the CPC 152. Alternatively, receive circuit 140B may provide an analog signal to CPC 152, and CPC 152 may convert the analog signal into a digital signal using an internal analog-to-digital converter (as described herein with reference to Figure 4 described above).

[0045] The CPC 152 may include circuitry capable of providing audio / self-test signals to the piezoelectric cantilever system 110, receiving electrical signals from the piezoelectric cantilever system 110 indicative of detection of acoustic waves, controlling various operating modes of the piezoelectric cantilever system 110, and providing processing functions related to the provided electrical drive signals or received response signals. In some examples, the CPC 152 may be part of an application specific integrated circuit (ASIC). In some examples, the CPC 152 may include one or more physical processor devices that execute instructions stored in a non-transitory memory to perform processing and control functions.

[0046] Each bimorph flap 102A and 102B may be configured to vibrate in response to an electrical drive signal or a pressure wave applied thereto. When electrically driven, one or more of the bimorph flaps 102A and 102B may be configured to vibrate in response to a corresponding electrical drive signal provided by CPC 152 (e.g., via transmit circuit 130A or 130B and switch circuit 120A or 120B). For example, CPC 152 may provide a first drive signal to bimorph flap 102A (via transmit circuit), wherein bimorph flap 102A is configured to vibrate at a first frequency in response to the first drive signal; and CPC 152 may provide a second drive signal to bimorph flap 102B, wherein bimorph flap 102B is configured to vibrate at a second frequency in response to the second drive signal. The first electrical drive signal and the second electrical drive signal may each have a corresponding response spectrum. In some cases, the corresponding response spectra of the first drive signal and the second drive signal may be substantially identical to each other. In certain other cases, the respective response spectra of the first drive signal and the second drive signal may be significantly different.

[0047] For example, when mechanically driven (e.g., by sound waves), one or more of the bimorph piezoelectric foils 102A and 102B can be configured to vibrate in response to the sound waves, thereby causing stress that is converted into an electrical signal that is provided to and received by the CPC 152 (e.g., via the switching circuit 120A or 120B and the receiving circuit 140A or 140B). Figure 2-Figure 5 Additional details regarding certain example operating modes are further explained.

[0048] Figure 2 yes Figure 1A and Figure 1B 1 is a block diagram of a portion of a piezoelectric cantilever system 110 in which a CPC 152 operates both bimorph flaps 102A and 102B according to a microphone mode. When operating according to the microphone mode, sound waves can pass through opening 106 toward bimorph flaps 102A and 102B. Bimorph flaps 102A and 102B vibrate in response to the sound waves, thereby causing stress that is converted into an electrical signal. The electrical signal generated by bimorph flap 102A is conducted to switching circuit 120A via terminals 170A and 172A. Through appropriate switch settings, switching circuit 120A conducts the converted electrical signal to receiver input terminals 142A-144A of receiving circuit 140A. Receive circuit 140A provides the electrical signal (generated by bimorph flap 102A) to CPC 152.

[0049] The electrical signal generated by the bimorph piezoelectric flap 102B is provided to the CPC 152 in a similar manner. The converted electrical signal can be propagated to the switch circuit 120B via terminals 170B and 172B. Through appropriate switch settings, the switch circuit 120B forwards the converted electrical signal to the receiver input terminals 142B-144B of the receiving circuit 140B. The receiving circuit 140B provides the electrical signal (generated by the bimorph piezoelectric flap 102B) to the CPC 152.

[0050] The CPC 152 may be further configured to perform various operations in response to receiving electrical signals from the receiving circuits 140A and / or 140B. For example, the CPC 152 may generate a response spectrum based on the received response signal, store data representing the response spectrum in a memory, compare the response spectrum to a reference spectrum, and provide a status indication based on the result of the comparison. Such a status indication may include, for example, one of the following: the presence of moisture on the bimorph piezoelectric foil 102A or 102B, the back volume of the piezoelectric cantilever system 110 separated from the opening 106 by the bimorph piezoelectric foil 102A and 102B (e.g., Figure 3 There is moisture in the rear volume 195), the mechanical integrity of the rear volume, and the distance of the gap / slit 118 between the dual piezoelectric chip wings 102A and 102B exceeds the limit.

[0051] Figure 3 1 is a block diagram of a portion of the piezoelectric cantilever system 110 of FIG. 1 , wherein the CPC 152 operates the bimorph flaps 102A and 102B according to a self-test mode. When operating in the self-test mode, the CPC 152 can provide a first electrical drive signal to the bimorph flap 102A via the transmitting circuit 130 and the switching circuit 120. In this example, by configuring the switching circuits 120A and 120B and making the bimorph flaps 102A and 102B independently controllable, the first electrical drive signal is not provided to the bimorph flap 102B. The bimorph flap 102A is configured to vibrate at a first frequency in response to the first provided electrical drive signal. The responsive vibration of the bimorph flap 102A creates a pressure / acoustic wave 350, which propagates toward the bimorph flap 102B via the back volume space 192.

[0052] The bimorph flap 102B vibrates in response to the acoustic / pressure waves generated by the electrically driven vibration of the bimorph flap 102A. The vibration of the bimorph flap 102B causes stress that is converted into an electrical signal. The electrical signal generated by the bimorph 102B is conducted to the switch circuit 120B via terminals 170B and 172B. Through appropriate switch settings, the switch circuit 120B conducts the frequency responsive electrical signal to the receiver input terminals 142B-144B of the receiving circuit 140B. The receiving circuit 140B provides the electrical signal (generated by the bimorph flap 102B) to the CPC 152.

[0053] The self-test operation may be performed for different characteristics of the piezoelectric cantilever system 110. In some examples, the self-test operation may be performed using a drive signal at a specific frequency to determine whether any of the tested bimorph flaps fails to vibrate and / or fails to generate an electrical signal at that frequency. In some examples, as described below, the CPC 152 may perform a self-test operation by providing drive signals at different frequencies (e.g., separated by specific frequency intervals based on a frequency sweep) to the bimorph flap 102A, which may vibrate to generate an acoustic wave. In some examples, the CPC 152 may provide different monotonic drive signals having different frequencies at different times. In some examples, the CPC 152 may also provide multi-tone drive signals having different frequencies. The CPC 152 may receive the electrical signals generated by the bimorph flap 102B in response to the acoustic waves at different frequencies, and perform processing to determine various frequency response characteristics of the piezoelectric cantilever system 110, such as a lower cutoff frequency, a resonant frequency, a quality factor, etc., as a result of the self-test operation. CPC 152 may compare the frequency response obtained from the self-test operation with a reference spectrum and provide a status indication based on the result of the comparison. Such status indication may include, for example, one of the following: the presence of moisture on bimorph flaps 102A or 102B, the presence of moisture in rear volume 192, the mechanical integrity of rear volume 192, or the gap distance between bimorph flaps 102A and 102B exceeds a limit.

[0054] In addition, the CPC 152 can perform additional processing operations based on the results of these self-test operations, such as determining equalization coefficients. When the piezoelectric cantilever system 110 is operated in the microphone mode, the CPC 152 can use the equalization coefficients to perform equalization operations on the electrical signals generated by the piezoelectric cantilever system 110 so that the conversion between the sound waves and the electrical signals of the audio device 100 can follow a specific response characteristic (e.g., a flat response across a specific frequency range, a peak response at a specific resonant frequency, a specific quality factor at the peak response, etc.).

[0055] Any suitable ratio of electrically driven bimorph flaps to mechanically driven bimorph flaps may be used to perform certain operations. Figure 4 Further described are example ratios of electrically driven bimorph flaps to mechanically driven bimorph flaps that may be applied to perform certain self-test modes of operation.

[0056] Figure 4 4 is another simplified system block diagram of the audio device 100. In this example, the audio device 100 includes a piezoelectric cantilever system 410, a switching circuit 420, a transmit circuit 430, a receive circuit 440, and a control and processing circuit ("CPC") 450.

[0057] In this example, piezoelectric system 410 is cylindrical in shape with four bimorph fins 402A, 402B, 402C, and 402D each extending toward the center. Bimorph fins 402A, 402B, 402C, and 402D are separated from each other by air gap slits that together form a cross shape. In some examples, piezoelectric system 410 may be Figure 1A and Figure 1B The piezoelectric cantilever system 110 of the embodiment of the present invention may be part of, or may include, the piezoelectric cantilever system 110. Each bimorph piezoelectric fin 402A, 402B, 402C, and 402D has a corresponding electrical interconnection with the switching circuit 420. The corresponding electrical interconnections between the bimorph piezoelectric fins 402A, 402B, 402C, and 402D and the switching circuit 420 may be electrically isolated from each other, so that each bimorph piezoelectric fin 402A, 402B, 402C, and 402D may be individually driven by a corresponding electrical signal, and each bimorph piezoelectric fin 402A, 402B, 402C, and 402D may transmit a corresponding electrical signal individually and independently.

[0058] Switching circuit 420 (may include Figure 1A and Figure 1B The switching circuits 120A and 120B (or may be part thereof) have a plurality of switches DA, DB, DC, DD, SA, SB, SC and SD. Although Figure 4 Each switch DA, DB, DC, DD, SA, SB, SC, and SD is shown as a single pole single throw (SPST) switch, but any suitable switch type(s) may be used. In this example, switches DA, DB, DC, and DD are opened or closed to enable CPC 450 to provide electrical drive signals to corresponding bimorph flaps 402A, 402B, 402C, and 402D, respectively, via transmit circuit 430. Switches SA, SB, SC, and SD are opened or closed to enable bimorph flaps 402A, 402B, 402C, and 402D to provide electrical signals to CPC 450 via receive circuit 440 in response to sound waves (or other mechanical vibrations).

[0059] Figure 4 The illustrated switch arrangement can implement different operations in the piezoelectric cantilever system 410. According to one arrangement, for example, CPC 450 closes switches DA, DB, and DC, and SD, and CPC 450 opens the remaining switches DD, SA, SB, and SC, so that CPC 450 can simultaneously provide an electrical drive signal to bimorph tabs 402A, 402B, and 402C without providing the same electrical drive signal to bimorph tab 402D. Such a switch arrangement can implement a self-test operating mode with a 3:1 ratio, in which bimorph tabs 402A, 402B, and 402C are electrically driven to vibrate at a resonant frequency in response to the electrical drive signal, and bimorph tab 402D generates an electrical signal by its vibration in response to a pressure wave created by the electrically driven vibration of bimorph tabs 402A, 402B, and 402C.

[0060] According to another example arrangement, CPC 450 closes switches DA, SB, SC, and SD, and CPC 450 opens the remaining switches DB, DC, DD, and SA, so that CPC 450 can provide an electrical drive signal only to bimorph piezoelectric foil 402A, and does not provide the same electrical drive signal to bimorph piezoelectric foils 402B, 402C, and 402D. Such an example arrangement of switches can implement a self-test operation mode with a 1:3 ratio, in which only bimorph piezoelectric foil 402A is electrically driven to vibrate at a resonant frequency in response to the electrical drive signal, and bimorph piezoelectric foils 402B, 402C, and 402D jointly generate an electrical signal (e.g., as the sum of the voltages between the middle electrode and the top / bottom electrode of each bimorph piezoelectric foil) in response to detecting the vibration of bimorph piezoelectric foil 402A.

[0061] As another example arrangement, CPC 450 closes switches DA, DB, SC, and SD, and CPC 450 opens switches DC, DD, SA, and SB, so that CPC 450 can provide an electrical drive signal only to bimorph flaps 402A and 402B, but not to bimorph flaps 402C and 402D. Such an arrangement of switches can implement a self-test operation mode with a 1:1 ratio, in which half of the bimorph flaps (in this example, bimorph flaps 402A and 402B) are electrically driven to vibrate at a specific frequency in response to the electrical drive signal, and the other half of the bimorph flaps (in this example, 402C and 402D) jointly generate an electrical signal in response to detecting the vibration of bimorph flaps 402A and 402B.

[0062] In an example microphone operation, CPC 450 may close switches SA, SB, SC, and SD, and CPC 450 may open the remaining switches DA, DB, DC, and DD. Under this type of switch arrangement, all bimorph flaps 402A, 402B, 402C, and 402D may be configured to generate corresponding electrical response frequency signals through their vibrations in response to pressure waves created by the surrounding environment. In some applications, this type of microphone operating mode may be considered a default operating mode.

[0063] Transmit circuit 430 may include any circuit system configured to receive the electrical drive signal from CPC 450 and provide it to switch circuit 420. In some examples, transmit circuit 430 may include multiple transmit circuits, such as reference Figure 1B The transmit circuit 430 may have one or more diodes that enable direct current to be transmitted in only one direction (e.g., from the CPC 450 toward the switch circuit 420). In an example speaker operation, the CPC 450 may close switches DA, DB, DC, and DD to drive the bimorph flaps 402A, 402B, 402C, and 402D.

[0064] Receive circuit 440 may include any circuitry configured to receive the electrical response frequency signal from one or more of bimorph piezoelectric foils 402A, 402B, 402C, or 402D (via switch circuit 420) and provide it to CPC 450. In some examples, receive circuit 440 may include multiple receive circuits, such as those described in reference to FIG. Figure 1B The transmit circuits 140A and 140B are further described in detail. The receive circuit 440 may have one or more diodes that enable direct current to be transmitted in only one direction (eg, from the switch circuit 420 toward the CPC 450).

[0065] CPC 450 includes an analog-to-digital converter ("ADC") 451, a digital signal processor ("DSP") 452, a non-volatile memory ("NVM") 454, and a digital control 455. In some examples, CPC 450 may include Figure 1B 450 may be part of CPC 152 such that ADC 451, DSP 452, NVM 454, and digital control 455 are all subcomponents of CPC 152. In some examples, CPC 450 may also include a not shown digital-to-analog converter ("DAC") coupled between digital control 455 and transmit circuit 430.

[0066] ADC 451 may include any circuit system configured to convert an analog electrical signal into a digital electrical signal. ADC 451 is communicatively coupled to receiving circuit 440 and digital control 455 so that ADC 451 can receive an analog electrical response frequency signal from receiver 440, convert it into a digital electrical signal, and provide the converted electrical signal to digital control circuit 455.

[0067] The digital control circuit 455 may include any circuitry configured to control the operation of certain other subcomponents of the piezoelectric cantilever system 400. The digital control circuit is communicatively coupled to at least the ADC 451, the DSP 452, the NVM 454, the transmit circuit 430, and the switch circuit 420. For example, by being communicatively coupled to the switch circuit 420, the digital control circuit 455 may be able to provide control signals to control the opening and closing of the switches DA, DB, DC, DD, SA, SB, SC, and SD. In addition, the digital control circuit 455 provides electrical drive signals to the switch circuit via the transmit circuit 430. As controlled by the digital control 455, the electrical drive signals are provided to the appropriate bimorph tabs 402A, 402D, 402C, and 402D in response to the arrangement of the switches DA, DB, DC, DD, SA, SB, SC, and SD within the switch circuit 420. In some examples, CPC 450 may include a DAC to convert a digital signal generated by digital control 455 into an analog electrical drive signal and provide the analog electrical drive signal to transmit circuit 430 .

[0068] DSP 452 may include any circuitry configured to perform one or more digital signal processing operations on data received from digital control 455 or NVM 454. For example, digital signal processing may involve performing Fourier transform operations to determine frequency response, and / or equalization operations as described herein. DSP 452 is communicatively coupled to at least digital control 455 and NVM 454. DSP 452 may provide equalized audio 453 as output.

[0069] NVM 454 refers to any suitable computer memory that can continuously store data or program code. The program code can provide computer readable instructions that, when executed, control the operation of one or more other components of CPC 450, such as digital control 455, ADC 451, or DSP 452. NVM 454 can be configured to store any suitable data. For example, the data stored by NVM 454 can be a digital representation of a response frequency signal received from piezoelectric cantilever system 410 via switch circuit 420, receiving circuit 440, ADC 451, and digital control 455. In addition, the data stored by NVM 454 can be a response spectrum stored as a digital representation of a collection of response frequency signals. As another example, the data stored by NVM 454 can be a digital representation of a target response spectrum that the piezoelectric cantilever system 410 is designed to achieve under optimal conditions and performance.

[0070] Figure 5 can be included in Figure 1A CPC 152 and Figure 4 4 is a block diagram of various subcomponents in the CPC 450 of FIG. In this example, the CPC includes a memory 510 storing self-test response data 520, a self-test module 530, an equalization module 540, and a self-cleaning module 550.

[0071] Memory 510 may include any suitable non-volatile computer memory that can persistently store data or program code. In some examples, memory 510 may be Figure 4 The data stored in the memory 510 includes at least the self-test response data 520. Figure 4 As explained, for example, certain self-test response data 520 stored in memory 510 may have been received from piezoelectric cantilever system 110 / 410 via switch circuit 420, receive circuit 440, ADC 451, and digital control 455. In some examples, memory 510 may also store program code to support self-test, equalization, and self-cleaning operations.

[0072] The self-test module 530 may include a circuit module configured to control the piezoelectric cantilever system 110 to perform one or more self-test operations to quantify one or more performance characteristics of the piezoelectric cantilever system. The self-test module 530 may also include program code (stored in the memory 510) that, when executed, causes the CPC and the piezoelectric cantilever system to perform one or more self-test operations. Figure 3-Figure 4As explained, for example, certain self-test mode operations may involve the CPC providing an electrical drive signal (via a transmitting circuit) to a first subset of one or more bimorph flaps (e.g., including at least bimorph flaps 102A, 402A, etc.). The first subset of bimorph flaps may vibrate in response to the first electrical drive signal. A second subset of one or more bimorph flaps (e.g., including at least bimorph flaps 102B, 402B, etc.) may be configured to vibrate in response to an acoustic wave created by the electrically driven vibration of the first subset of bimorph flaps. The mechanically driven vibration of the second subset of bimorph flaps generates a second electrical signal. In some examples, the CPC may provide drive signals at different frequencies to the first subset of bimorph flaps, and the electrical signals generated by the second subset of bimorph flaps (representing the vibration caused by the acoustic wave) may be processed by the CPC to generate a frequency response of the piezoelectric cantilever system 110 (or 410).

[0073] The CPC may further determine one or more operational characteristics of the piezoelectric system 110. For example, the CPC may determine whether the second subset of bimorph flaps vibrated as expected in response to the acoustic waves generated by the first subset of bimorph flaps by comparing the amplitude / magnitude / frequency of the second electrical signal to a corresponding threshold amplitude / magnitude / frequency. If the amplitude / magnitude / frequency of the second electrical signal is below the corresponding threshold, the CPC may determine that the second subset of bimorph flaps failed to vibrate.

[0074] Furthermore, by comparing frequency response characteristics, such as lower cutoff frequency, resonant frequency, quality factor (Q factor), etc., from the measured frequency response of the piezoelectric cantilever system 110 and their target values ​​(stored in the memory 510), it can be determined whether the processed data indicates that the piezoelectric cantilever system 110 is operating within expected specifications, or alternatively, one or more possible fault conditions may be indicated. Example fault conditions that may be indicated include: the bimorph flaps are not vibrating in response to the acoustic waves, the presence of moisture on one or more bimorph flaps (e.g., bimorph flaps 102A and 102B), the presence of moisture in the back volume 195 separated from the opening 106 by one or more bimorph flaps (e.g., bimorph flaps 102A and 102B), or the gap / slit 118 distance between the first bimorph flap and the second bimorph flap exceeds a limit.

[0075] The CPC can perform actions in response to detecting a fault condition. For example, in the event that the fault is not correctable (e.g., the bimorph flap does not vibrate, the distance of the gap / slit 118 exceeds a limit, etc.), the CPC can provide a signal indicating the fault condition, disable the receiving circuit (or the entire audio device), etc. In the event that the fault is correctable (e.g., the presence of moisture or other foreign matter), the CPC can trigger the self-cleaning module 550 to begin a self-cleaning operation to correct the fault, as described below.

[0076] The CPC can be configured to execute the self-test module 530 throughout the life of the piezoelectric cantilever system 110. For example, the self-test module 530 can be executed as part of an initialization process each time the piezoelectric cantilever system 110 is used or powered on. Repeated execution of the self-test module 530 can provide real-time insight into certain operating conditions of the piezoelectric cantilever system 110, which can provide early warning that the self-cleaning module 550 should be executed or that an update of the equalization data stored in the memory 510 and used by the equalization module 540 may be required. Such cooperative operation of the modules 530, 540, and 550 can improve the reliability, life, and operational fidelity of the piezoelectric cantilever system 110.

[0077] The equalization module 540 may include a circuit module configured to perform one or more self-equalization operations on the piezoelectric cantilever system 110. The equalization module 540 may also include program code (stored in the memory 510) that, when executed, causes the CPC to perform one or more self-equalization operations on the piezoelectric cantilever system 110. In some applications, it may be desirable to minimize any sensitivity variation of a given piezoelectric cantilever system 110 across its operating frequency range. Certain digital signal processing (e.g., performed by the DSP 452) performed when the equalization module 540 is executed may be used to counteract known sensitivity variations across the operating frequency range. Such digital signal processing may improve the ability of the piezoelectric microphone 110 to sense all relevant frequencies of the operating range with the same or substantially similar weighting, which may improve the ability of the piezoelectric cantilever system 110 to record acoustic input (as a microphone) or provide high fidelity acoustic output (as a speaker).

[0078] The equalization module 540 can access the self-test response data 520 from the memory 510. The self-test response data 520 can be generated by the self-test module 530 when the piezoelectric cantilever system 110 is operated in the self-test mode. The CPC can use the accessed data when applying certain digital signal processing (e.g., using the DSP 452). As described above, during the self-test operation, the self-test module 530 can scan the frequency of driving the first subset of bimorph blades, and the voltage output by the second subset of the piezoelectric bimorphs can be sampled and converted into digital values. The self-test response data 520 can include a set of digital values ​​mapped to different frequencies. The digital signal processing can include determining the sensitivity of the piezoelectric microphone 110 at different frequencies based on the digital values. The sensitivity can be the ratio between the voltage output by the second subset of bimorph blades and a predetermined pressure value caused by the sound waves generated by the first subset of bimorph blades (e.g., based on the amplitude of the sound waves, the back volume space, etc.).

[0079] The digital signal processing may also include determining various frequency response characteristics of the piezoelectric microphone 110 based on the sensitivity, such as a lower cutoff frequency and a resonant frequency. For example, the equalization module 540 may determine the sensitivity of the piezoelectric microphone 110 at a particular frequency (e.g., 1 kHz) as a nominal value, and normalize the sensitivity at other frequencies relative to the nominal value. The equalization module 540 may determine the lower cutoff frequency as the frequency at which the sensitivity rolls off from 0 dB (nominal value), the resonant frequency as the frequency at which the sensitivity reaches a peak, the Q factor as the frequency range over which the sensitivity experiences a 3 dB reduction from the peak sensitivity, and so on. The equalization module 540 may also determine an equalization coefficient that may be used in conjunction with the digital samples received from the piezoelectric cantilever system 110 when operating in microphone mode, or may be used to generate a processed audio signal for the transmit circuit 430 when operating in speaker mode to correct for sensitivity variations with frequency.

[0080] Specifically, the equalization coefficients may provide an increased amplification gain at frequencies close to the lower cutoff frequency and a reduced amplification gain at frequencies close to the resonant frequency to provide uniform sensitivity across a frequency range (e.g., an audible frequency range). During microphone operation, the equalization module 540 may perform a transform operation (e.g., a Fourier transform) to convert digital samples from a time domain to a frequency domain, apply frequency-dependent equalization coefficients to the digital samples in the frequency domain, and convert the digital samples from the frequency domain back to the time domain to generate a balanced audio signal. In addition, during speaker operation, the equalization module 540 may also perform a transform operation (e.g., a Fourier transform) to convert a digital audio signal from a time domain to a frequency domain, apply frequency-dependent equalization coefficients to the digital audio signal in the frequency domain, and convert the digital audio signal from the frequency domain back to the time domain to generate a balanced digital audio signal. The DAC may then convert the balanced digital audio signal into an electrical drive signal from the transmit circuit 430.

[0081] Figure 6 6 is a graph 600 that plots example response spectra 610, 620, and 630 of the piezoelectric cantilever system 110 to illustrate the equalization operation performed by the equalization module. Each response spectrum represents the relationship between the voltage (in dBV) provided by the piezoelectric cantilever system 110 in response to an acoustic wave and the frequency of the acoustic wave. The acoustic wave exerts a specific pressure (e.g., 1 Pa) on the piezoelectric bimorph, and the response (in terms of voltage / pressure) can represent the sensitivity of the piezoelectric cantilever system. The response spectrum 610 represents the actual frequency response of the piezoelectric cantilever system 110 when operating in microphone mode, where all bimorph fins vibrate in response to the acoustic wave, and the voltage output by the piezoelectric cantilever system can be the sum of the voltages output by each bimorph fin in response to the vibration. The response spectrum 610 can represent the relationship between the sensitivity (based on the sum of the voltages output by the bimorphs) and the frequency of the acoustic wave detected by the microphone. In addition, the response spectrum 620 represents a measured frequency response of the piezoelectric cantilever system 110 when operating in a self-test mode, wherein the CPC transmits a drive signal to vibrate a first subset (e.g., a first half) of the piezoelectric bimorphs to generate an acoustic wave, and a second subset (e.g., a second half) of the piezoelectric bimorphs vibrates in response to the acoustic wave and generates an electrical signal in response to stress caused by the vibration. The response spectrum 620 may represent a relationship between the sensitivity of the second subset of piezoelectric bimorphs (based on the sum of the voltages output by the subset of bimorphs) and the frequency of the acoustic wave generated in the self-test mode.

[0082] In addition, response spectrum 630 represents a normalized version of response spectrum 620, where the measured sensitivities at different frequencies are normalized to the measured sensitivity at a specific frequency, such as 1 kHz. Due to the normalization, response spectrum 630 may align / overlap with response spectrum 610 over a specific frequency range, such as in a low frequency range close to a lower cutoff frequency. Figure 6 As shown, measured response spectrum 630 has a similar cutoff frequency (e.g., 30 Hz, labeled by label 640) as actual response spectrum 610. In addition, measured response spectrum 630 has a similar peak / resonant frequency (e.g., 60 kHz, labeled by labels 650, 660, and 670) as actual response spectrum 610. However, measured response spectrum 630 has a reduced quality (Q) factor compared to actual response spectrum 610, such that measured response spectrum 630 has a broader response peak than actual response spectrum 610.

[0083] As described above, it may be desirable to minimize any sensitivity variation of a given piezoelectric cantilever system 110 across its operating frequency range. The desired / target frequency response of the piezoelectric cantilever system 110 may include a uniform sensitivity (e.g., 0 dBV re 1 Pa) across a large portion of the human audible frequency range (e.g., approximately 20 Hz to 20 kHz). Therefore, in order to provide uniform sensitivity, the equalization module 540 may determine a set of equalization coefficients and scale the sampled signal with the equalization coefficients. Specifically, the equalization coefficients may provide an increased amplification gain at frequencies close to a lower cutoff frequency and a reduced amplification gain at frequencies close to a resonant frequency. As described above, the measured response spectrum 630 may provide an accurate representation of the lower cutoff frequency and the resonant frequency of the piezoelectric cantilever system 110. Therefore, the equalization module 540 may determine the lower cutoff frequency and the resonant frequency of the piezoelectric cantilever system 110 from the measured response spectrum 630 and determine the equalization coefficients accordingly. For example, based on the measured response spectrum 630, the equalization module 540 can determine the frequency as the lower cutoff frequency based on the sensitivity at the frequency (e.g., 30 Hz) at the tag 640 decreasing by 3 dB relative to the nominal sensitivity (0 dBV). The equalization module 540 can also determine the frequency at the tag 670 (e.g., 60 kHz) as the resonant frequency based on the sensitivity reaching a peak at the frequency.

[0084] Additionally, the self-test module 530 can determine the Q factor of the piezoelectric cantilever system 110 based on the measured response spectrum 630 and compare it to a reference Q factor and determine whether the measured Q factor is reduced. A reduction in the measured Q factor relative to the reference Q factor can indicate any of a number of negative operating conditions of the piezoelectric cantilever system 110. For example, the presence of moisture or particles can cause increased air friction between the bimorph tabs (e.g., at the air gap slit 104), which can be detected by a reduction in the measured Q factor.

[0085] Additionally, the lower cutoff frequency and resonant frequency obtained through certain self-test operations may provide insight into certain operating conditions and physical states of the piezoelectric cantilever system 110 under test. For example, a measured resonant frequency that deviates significantly from a reference resonant frequency may indicate the presence of moisture or other unexpected material on one or more bimorph tabs (e.g., bimorph tabs 102A and 102B) of the piezoelectric cantilever system 110 under test, the presence of moisture between the back volume (e.g., back volume 195) and the bimorph tabs (e.g., bimorph tabs 102A and 102B) of the piezoelectric cantilever system 110 under test, the mechanical integrity of the back volume itself, the gap distance between the bimorph tabs (e.g., bimorph tabs 102A and 102B) exceeding a limit, etc.

[0086] Reference again Figure 5 , the self-cleaning module 550 may include a circuit module configured to control the piezoelectric cantilever system 110 to perform one or more self-cleaning operations. The self-cleaning module 550 may also include a program code (stored in the memory 510) that, when executed, causes the CPC to perform one or more self-cleaning operations. The self-test module 530 may trigger the self-cleaning module 550 to start self-cleaning in response to detecting a foreign object (e.g., moisture) based on, for example, detecting a large deviation in the resonant frequency, the lower cutoff frequency, etc., as described above. The self-cleaning module 550 may perform a self-cleaning operation, for example, by driving the bimorph flaps (including the bimorph flaps 102A and 102B) of the piezoelectric cantilever system 110 at the resonant frequency of the bimorph flaps (determined by the self-test module 530) to maximize / increase the amplitude of the vibration to remove particles / moisture, and minimize / reduce the amount of driving power, which may improve the efficiency of the self-cleaning operation. As described above, the self-cleaning module 550 may also enable the heater 194 to heat and evaporate any moisture present in the rear volume 192 and / or the front volume.

[0087] Figure 7 A flow chart of an example method 700 of operating a piezoelectric audio device, such as the audio device 100, including a piezoelectric cantilever system, such as the piezoelectric cantilever system 110, 410, or other cantilever systems described below, is shown. The method 700 may be performed by, for example, the CPC 152 / 450 in conjunction with the piezoelectric cantilever system. The method 700 may be operated by the audio device 100 configured as a microphone or a speaker.

[0088] In operation 702, the CPC may drive a first piezoelectric flap (e.g., bimorph flap 102A, 402A) of an audio device with a first electrical signal via a transmitting circuit (e.g., transmitting circuit 130A, 430, etc.) to generate an acoustic signal / sound wave. The first electrical signal (and acoustic signal) may be monophonic and have a specific frequency, or may be polyphonic and have a set of frequencies. The sound wave may propagate to a second piezoelectric flap (e.g., bimorph flap 102B, 402B) of the audio device via the back volume 192. Some of the sound waves may also propagate directly from the first piezoelectric flap to the second piezoelectric flap via the back volume.

[0089] In operation 704, the CPC may receive a second electrical signal from a second piezoelectric bimorph of the audio device in response to the acoustic signal. The second piezoelectric bimorph may vibrate in response to the acoustic signal, and the vibration creates stress. The second piezoelectric bimorph may generate a second electrical signal representing the stress (e.g., a voltage between the middle electrode and the top / bottom electrode). The CPC may receive the second electrical signal via a receiving circuit (e.g., receiving circuit 140B, 440, etc.).

[0090] The CPC may determine a characteristic of the audio device based on the second electrical signal in operation 706. The CPC may sample and digitize the second electrical signal and determine the characteristic based on the digital samples.

[0091] In some examples, the characteristic may include a state of the piezoelectric cantilever system (e.g., whether some or all of the piezoelectric flaps under test fail to vibrate in response to the acoustic signal). For example, if the second electrical signal received by the CPC has an amplitude (or magnitude) less than a threshold, and / or if the frequency of the second electrical signal does not match the frequency of the first electrical signal (within a certain tolerance), the CPC may determine that at least some of the piezoelectric flaps under test have failed.

[0092] In some examples, the characteristic may also include a frequency response of the piezoelectric cantilever system, for example, the CPC may determine the relationship between the sensitivity and frequency, the lower cutoff frequency, the resonant frequency, etc. of the piezoelectric cantilever system based on the frequency response. As described above, the CPC may drive the first piezoelectric foil with a multi-tone drive signal, or drive the first piezoelectric foil with a single-tone drive signal having different frequencies at different times. The CPC may process the digital samples of the second electrical signal and generate a response spectrum that maps the sensitivity to different frequencies, such as Figure 6 The response spectrum shown is 630. The CPC can also determine the lower cutoff frequency, resonant frequency, Q factor, etc. based on the response spectrum.

[0093] In operation 710, the CPC may perform an action based on the characteristic. For example, in the event that an uncorrectable fault is detected (e.g., the piezoelectric flap fails to vibrate, the gap / slit 118 becomes too large), the CPC may output a signal indicating the fault, disable some or part of the audio device to prevent the faulty piezoelectric cantilever system from generating an audio signal, etc. In addition, in the event that a correctable fault is detected, such as the presence of foreign matter, moisture, etc., the CPC may initiate a self-cleaning module 550 to begin a self-cleaning operation (e.g., by driving the piezoelectric flap at a resonant frequency) to remove the foreign matter / moisture. In addition, the CPC may determine a set of equalization coefficients based on the identification of the lower cutoff frequency and the resonant frequency, and the equalization module 540 may use the set of equalization coefficients to perform an equalization operation on future digital samples received from the piezoelectric cantilever system when operating in microphone mode or future audio signals to be output by the piezoelectric cantilever system when operating in speaker mode.

[0094] Fig. 8A A cross-sectional view 800 of an alternative piezoelectric system 810 is shown. In some examples, the piezoelectric cantilever system 810 can be used as the piezoelectric cantilever system 110 / 410 in the audio device 100. The illustrated cross-sectional view 800 of the piezoelectric cantilever system 810 includes two bimorph fins 802A-802B with a gap / slit 118 separating the bimorph fin 802A from an adjacent bimorph fin 802B. Although the illustrated cross-sectional view 800 of the piezoelectric cantilever system 810 shows two bimorph fins 802A-802B, the piezoelectric cantilever system 810 can include at least four bimorph fins (e.g., Figure 8B shown).

[0095] Bimorph tabs 802A and 802B are formed on structure 114. Substrate 114 has openings 106 formed therethrough that allow pressure waves to be transmitted to or from bimorph tabs 802A and 802B through openings 106. Both bimorph tabs 802A and 802B are cantilevered such that respective fixed portions are on structure 114 and respective movable portions extend over respective portions of opening 106.

[0096] Each bimorph fin 802A-802B has a multi-layer structure. Fig. 8AAs shown, the bimorph fin 802A has a top electrode 860A, an intermediate electrode 862A, and a bottom electrode 864A. At least a portion of the intermediate electrode 862A is located between the top electrode 860A and the bottom electrode 864A. The bimorph fin 802A also has a first piezoelectric layer 880A and a second piezoelectric layer 882A. The piezoelectric layer 880A has at least a portion between the top electrode 860A and the intermediate electrode 862A. The piezoelectric layer 882A has at least a portion between the intermediate electrode 162A and the bottom electrode 864A. The top electrode 860A and the bottom electrode 864A are coupled to a terminal 870A. The intermediate electrode 862A is coupled to another terminal (e.g., similar to the terminal 170B of FIG. 1).

[0097] The bimorph fin 802B has a top electrode 860B, an intermediate electrode 862B, and a bottom electrode 864B. At least a portion of the intermediate electrode 862B is located between the top electrode 860B and the bottom electrode 864B. The bimorph fin 802B also has a first piezoelectric layer 880B and a second piezoelectric layer 882B. The piezoelectric layer 880B has at least a portion between the top electrode 860B and the intermediate electrode 862B. The piezoelectric layer 882B has at least a portion between the intermediate electrode 862B and the bottom electrode 864B. The top electrode 860B and the bottom electrode 864B are coupled to the terminal 772B. The intermediate electrode 862B is coupled to another terminal (e.g., similar to the terminal 170B of FIG. 1 ).

[0098] exist Fig. 8A In the embodiment of the present invention, the length of electrodes 860A-860B, 862A-862B, and 864A-864B only extends through one-quarter to one-half of the portion of the piezoelectric bimorph suspended above opening 106. The exact ratio can be determined based on various factors, such as the material of the electrodes, the piezoelectric material, and the output energy (from the vibration). In some examples, the ratio can be selected to maximize the output energy. Fig. 8A As shown, the suspended portion of the bimorph 802A has one end 807A on the oxide 193 and an opposite end 808A above the opening 806. At least one of the top electrode 860A, the middle electrode 862A, or the bottom electrode 864A each extends from the end 807B no more than half of the distance between the ends 807A and 808A. In addition, the suspended portion of the bimorph 802B has one end 807B on the oxide 193 and an opposite end 808B above the opening 106. At least one of the top electrode 860B, the middle electrode 862B, or the bottom electrode 864B each extends no more than half of the distance between the ends 807B and 808B. Each electrode extends between one quarter (1 / 4) and one half (1 / 2) of the distance between the ends 807A and 808A and between the ends 807B and 808B.

[0099] exist Fig. 8A In the piezoelectric cantilever system 810 of FIG. 8 , the middle electrode 862A does not extend to the end 808A, and the middle electrode 862B does not extend to the end 808B. In this example configuration, the piezoelectric layers 880A and 882A are in direct contact with each other at the end 808A; and the piezoelectric layers 880B and 882B are in direct contact with each other at the end 808B.

[0100] Figure 8B Shows Fig. 8A 808A. The different shading of end 807A relative to end 808A shows that the outermost top electrode 860A extends from end 807A to point 809A, which in this example does not exceed half of the distance between ends 807A and 808A. Similarly, the different shading of end 807B relative to end 808B shows that the outermost top electrode 860B extends from end 807B to point 809B, which in this example does not exceed half of the distance between ends 807B and 808B. The partial coverage of the top electrodes 806A-806B exposes the outer surface of the piezoelectric layer 880A-880B or 882A-882B (e.g., along the surface extending from 809A to 809B). In this example, the length of the exposed surface piezoelectric layer surface (eg, measured between ends 808A and 809A and between 808B and 809B) is greater than half the length of the suspended portion of the corresponding piezoelectric bimorph tab.

[0101] although Figure 8B The piezoelectric cantilever system 810 is shown as having four bimorph fins 802A, 802B, 802C, and 802D, but the piezoelectric cantilever system 810 may include fewer bimorph fins (e.g., 2 or 3) or more bimorph fins (e.g., 5, 6, 7, 8, 9, 10, 11, 12, or more). In addition, although Figure 8B The piezoelectric cantilever system 810 is illustrated as having a cylindrical shape, but the piezoelectric cantilever system 810 may have any suitable shape (eg, a three-dimensional extruded shape of an ellipse, square, rectangle, triangle, trapezoid, some other polygon, etc.).

[0102] The piezoelectric cantilever system 810 can also have any suitable dimensions. For example, the piezoelectric cantilever system 810 can have a maximum width (e.g., measured from end 807A to 807B) of 500 microns to 1 millimeter and a maximum height of 250 microns to 0.5 millimeters, where the maximum height is, for example, no greater than half of the maximum width. In some examples, each air gap slit (e.g., gap / slit 118) separating the bimorph tabs 802A, 802B, 802C, and 802D from each other can have a width in the range of 1 to 10 microns.

[0103] Fig. 8A and Figure 8B The arrangement can reduce the overall mass / weight of each piezoelectric bimorph, which can facilitate the movement of the bimorph in response to sound waves and increase the overall sensitivity of the audio device in detecting sound waves and converting sound waves into electrical signals. Specifically, during the movement of the bimorph, the stress (and electric field) at the ends 807A and 807B of the bimorph is much higher than that at the ends 808A and 808B of the bimorph. Therefore, the electrodes at the ends 807A and 807B can sense a larger electric field / stress per unit movement of the bimorph, but the electrodes toward the center at the ends 807B and 808B can sense a reduced electric field / stress and will not improve the overall sensing output of the bimorph. At the same time, by removing the electrodes at the ends 807B and 808B, the mass / weight of the bimorph can be reduced, which can improve the overall sensitivity of the audio device in converting between sound waves and electrical signals. Furthermore, a reduction in the overall mass of the bimorph piezoelectric foil may shift the resonant frequency (eg, toward the audible frequency range) and reduce residual stresses, which may also affect the sensitivity of the bimorph piezoelectric foil.

[0104] Fig. 9A and Fig. 9B A perspective view 900 and a cross-sectional view 950 are provided, respectively, of a portion of a piezoelectric cantilever system 910 having a plurality of bimorph fins including at least Fig. 9A , the bimorph fins 902A and 902B are separated from each other by gap / slit 118. The cantilever system 910 may be Fig. 8A and Figure 8B An example of a cantilever system 810 .

[0105] refer to Fig. 9A and Fig. 9B, the bimorph fin 902B has a top electrode 960B, an intermediate electrode 962B, and a bottom electrode 964B. At least a portion of the intermediate electrode 962B is located between the top electrode 960B and the bottom electrode 964B. The bimorph fin 902B also has a first piezoelectric layer 980B and a second piezoelectric layer 982B. The piezoelectric layer 980B has at least a portion between the top electrode 960B and the intermediate electrode 962B. The piezoelectric layer 982B has at least a portion between the intermediate electrode 962B and the bottom electrode 964B. In addition, at least a portion of the bottom electrode 964B is embedded in the piezoelectric layer 982B, wherein the surface 960 of the bottom electrode 964B and the surface 962 of the piezoelectric layer 982B are continuous and conformal to each other.

[0106] like Fig. 9B As shown, the suspended portion of the bimorph fin 902B has one end 907B on the structure 114, and another end 808B above the opening in the structure 114. The top electrode 960B, the middle electrode 962B, and the bottom electrode 964B each extend from the end 907B to no more than three quarters of the distance between the ends 907B and 908B. A portion of the middle electrode 962B is located between the piezoelectric layers 980B and 982B at the end 907B. The middle electrode 962B does not extend completely from the end 907B to the end 908B, so that the piezoelectric layers 980B and 982B are in direct contact with each other from the end 908B to where the middle electrode 962B terminates.

[0107] In some examples, bimorph fin 902B can have a reduced overall thickness at end 908B relative to the overall thickness of bimorph fin 902B at end 907B, which can result in a reduced overall mass of bimorph fin 902B. As described above, the reduction in the overall mass of bimorph fin 902B can provide certain technical advantages in some applications. For example, the reduction in the overall mass of bimorph fin 902B can result in an increase in the resonant frequency of bimorph fin 902B. In addition, the reduction in the overall mass of bimorph fin 902B can alleviate residual stresses that affect the performance of bimorph fin 902B.

[0108] Fig. 10A The manufacture of a piezoelectric cantilever system (such as Fig. 9A and Fig. 9B Flowchart of an example method 1000 of a piezoelectric cantilever system 910). In addition, Figure 10B-Figure 10F Shown in Fig. 10A Piezoelectric cantilever system at various stages of fabrication shown.

[0109] refer to Fig. 10A and Fig. 10BIn operation 1002, a first electrode (e.g., bottom electrode 964B) is formed on an outer surface of a multilayer substrate (e.g., substrate 990), which may include an oxide layer and a semiconductor (e.g., silicon) substrate. The bottom electrode extends over position 992 to position 994 of the multilayer substrate 990, wherein positions 992 and 994 may correspond to, for example, ends 907B and 908B of a suspended portion of a piezoelectric bimorph fin 902B, respectively, which includes a bottom electrode to be formed in a subsequent operation. The bottom electrode may have a length between half and one-quarter of the distance between positions 992 and 994. The portion of the substrate 990 between positions 992 and 994 below the bottom electrode will be removed in a subsequent operation to form the opening 106 and the structure 114. For example, the formation of the shown portion of the bottom electrode 964B may be performed by sputtering a molybdenum layer on the substrate 990. The molybdenum layer may then be patterned, etched, and cleaned to form the illustrated portion of the bottom electrode 964B, wherein the bottom electrode 964B extends no more than half the distance between locations 992 and 994 (and ends 907B and 908B).

[0110] refer to Fig. 10A and Fig. 10C In operation 1004, a first piezoelectric layer (e.g., piezoelectric layer 982B) is formed on the bottom electrode 964B and the corresponding portion of the substrate 990. The formation of the illustrated piezoelectric layer 982B may be performed, for example, by sputtering deposition of a piezoelectric material layer (such as an AlN layer). The deposition of the piezoelectric layer 982B may be substantially conformal to the underlying layers, such that a portion of the piezoelectric layer 982B above the bottom electrode 864B may have a slight height difference relative to a portion of the piezoelectric layer 982B in contact with the substrate 890, and at least a portion of the bottom electrode 964B may be embedded in the piezoelectric layer 982B.

[0111] refer to Fig. 10A and Fig. 10D , in operation 1006, a second electrode (e.g., intermediate electrode 862B) is formed on the first piezoelectric layer (e.g., piezoelectric layer 882B). The intermediate electrode also extends over position 992 to position 994 of the multilayer substrate 990, and the intermediate electrode can have a length between half and one-quarter of the distance between positions 992 and 994 (and ends 907B and 908B). For example, the formation of the shown portion of the intermediate electrode 962B can be performed by sputtering deposition of a molybdenum layer. The molybdenum layer can then be patterned, etched, and cleaned to form the shown portion of the intermediate electrode 962B, wherein the intermediate electrode 962B extends no more than half of the distance between positions 992 and 994 (and ends 907B and 908B).

[0112] refer to Fig. 10A and Fig.10E In operation 1008, a second piezoelectric layer (e.g., piezoelectric layer 980B) may be formed on the second electrode (e.g., middle electrode 962B) and corresponding portions of the first piezoelectric layer (e.g., piezoelectric layer 982B). The formation of the piezoelectric layer 980B shown may be performed by, for example, sputtering deposition of an AlN layer. The deposition of the piezoelectric layer 980B may be substantially conformal to the underlying layers, such that a portion of the piezoelectric layer 980B above the middle electrode 962B may have a slight height difference relative to a portion of the piezoelectric layer 980B contacting the piezoelectric layer 982B.

[0113] refer to Fig. 10A and Fig.10F , in operation 1010, a third electrode (e.g., top electrode 860B) is formed on the second piezoelectric layer (e.g., piezoelectric layer 980B). The top electrode also extends over position 992 to position 994 of the multilayer substrate 990, and the top electrode can have a length between half and one-quarter of the distance between positions 992 and 994 (and ends 907B and 908B). The formation of the shown portion of the top electrode 960B can be performed by, for example, sputtering deposition of a molybdenum layer. The molybdenum layer can then be patterned, etched, and cleaned to form the shown portion of the top electrode 960B, wherein the top electrode 960B extends no more than half of the distance between positions 992 and 994 (and ends 907B and 908B).

[0114] refer to Fig. 10A and Figure 10G , in operation 1012, a portion of substrate 990 between locations 992 and 994 may be removed to form structure 114 and opening 106. Removal of the portion of substrate 990 may be performed, for example, by a backside etching process operation. Additionally, bimorph tab 902B may be separated by an adjacent bimorph tab (e.g., bimorph tab 902A) by completely etching through at least respective portions of piezoelectric layers 980B and 982B proximate end 908B, thereby forming gap / slit 118.

[0115] Fig.11A and Fig. 11B A perspective view 1100 and a cross-sectional view 1150 of a portion of another example of a piezoelectric cantilever system 910 are provided, respectively. The example piezoelectric cantilever system 910 has Fig. 9A and Fig. 9BThe example piezoelectric cantilever system has a similar arrangement of electrodes and piezoelectric layer 982B, where the top electrode 960B covers at least a portion of the piezoelectric layer 980B. The piezoelectric layer 980B extends no more than half of the distance between the ends 907B and 908B, and the middle electrode 962B covers at least a portion of the piezoelectric layer 982B. The top electrode 960B and the middle electrode 962B extend no more than half of the distance from the end 907B to the end 908B. The piezoelectric layer 982B extends completely from the end 907B to the end 908B, and therefore has an exposed surface extending from where the middle electrode 962B terminates to the end 908B.

[0116] The top electrode 960B, the middle electrode 962B, and the bottom electrode 964B extending from the end 907B to no more than half the distance between the ends 907B and 908B can result in a reduced overall mass of the bimorph fin 902B (e.g., relative to an alternative bimorph fin in which the top electrode, the middle electrode, and the bottom electrode extend completely end-to-end). Fig. 11B As shown, by removing a portion of the piezoelectric layer 980B, the Fig. 11B The total mass of the bimorph fin 902B shown in FIG. 902B. The reduction in the total mass of the bimorph fin 902B can result in an increase in the sensitivity of the bimorph fin 902B. In addition, the reduction in the total mass of the bimorph fin 902B can alleviate residual stresses that affect the performance of the bimorph fin 802B.

[0117] Fig. 12A The manufacture of a piezoelectric cantilever system (such as Fig.11A and Fig. 11B Flowchart of an example method 1200 of a piezoelectric cantilever system 910). In addition, Figure 12B-12I Shown in Fig. 12A Piezoelectric cantilever system shown in various stages of fabrication.

[0118] refer to Fig. 12A and Fig. 12BIn operation 1202, a first electrode (e.g., bottom electrode 964B) is formed on an outer surface of a multilayer substrate (e.g., substrate 990), which may include an oxide layer and a semiconductor (e.g., silicon) substrate. The bottom electrode extends over position 992 to position 994 of the multilayer substrate 990, wherein positions 992 and 994 may correspond to, for example, ends 907B and 908B of a suspended portion of a piezoelectric bimorph fin 902B, respectively, which includes a bottom electrode formed in a subsequent operation. The bottom electrode may have a length between half and one-quarter of the distance between positions 992 and 994. The portion of the substrate 990 between positions 992 and 994 below the bottom electrode will be removed in a subsequent operation to form the opening 106 and the structure 114. For example, the formation of the shown portion of the bottom electrode 964B may be performed by sputtering a molybdenum layer on the substrate 990. The molybdenum layer may then be patterned, etched, and cleaned to form the illustrated portion of the bottom electrode 964B, wherein the bottom electrode 964B extends no more than half the distance between locations 992 and 994 (and ends 907B and 908B).

[0119] refer to Fig. 12A and Fig. 12C In operation 1204, a first piezoelectric layer (e.g., piezoelectric layer 982B) is formed on the bottom electrode 964B and the corresponding portion of the substrate 990. The formation of the illustrated piezoelectric layer 982B may be performed, for example, by sputtering deposition of a piezoelectric material layer (such as an AlN layer). The deposition of the piezoelectric layer 982B may be substantially conformal to the underlying layers, such that a portion of the piezoelectric layer 982B above the bottom electrode 964B may have a slight height difference relative to a portion of the piezoelectric layer 982B in contact with the substrate 890, and at least a portion of the bottom electrode 964B may be embedded in the piezoelectric layer 982B.

[0120] refer to Fig. 12A and Fig.12D In operation 1206, a second electrode (e.g., middle electrode 862B) is formed on the first piezoelectric layer (e.g., piezoelectric layer 882B). The middle electrode also extends from position 992 to position 994 of the multilayer substrate 990. Fig.12D , the intermediate electrode may extend over the entire length between locations 992 and 994 (and ends 907B and 908B). For example, the formation of the shown portion of the intermediate electrode 962B may be performed by sputtering deposition of a molybdenum layer.

[0121] refer to Fig. 12A and Fig.12EIn operation 1208, a second piezoelectric layer (eg, piezoelectric layer 980B) may be formed on the second electrode (eg, the middle electrode 962B). The formation of the piezoelectric layer 980B may be performed, for example, by sputtering deposition of an AlN layer.

[0122] refer to Fig. 12A and Fig.12F In operation 1210, a portion of the second piezoelectric layer (e.g., piezoelectric layer 980B) on the second electrode (e.g., middle electrode 962B) is removed and a portion of the middle electrode 962B below is exposed. The selective removal of portions of the piezoelectric layer 980B may be performed, for example, by one or more patterning, etching, and cleaning processes. Half (or more) of the piezoelectric layer 980B between positions 992 and 994 may be removed.

[0123] refer to Fig. 12A and Figure 12G , in operation 1212, the exposed portion of the second electrode (e.g., the middle electrode 962B) is removed. For example, the selective removal of a portion of the middle electrode 962B can be performed by one or more patterning, etching, and cleaning processes. After selectively removing the portion of the middle electrode 962B, the remaining portion of the middle electrode 962B extends no more than half of the distance between the positions 992 and 994 (and the ends 907B and 908B).

[0124] refer to Fig. 12A and Fig.12H , in operation 1214, a third electrode (e.g., top electrode 960B) is formed on the remaining second piezoelectric layer (e.g., piezoelectric layer 980B). The top electrode also extends over position 992 to position 994 of the multilayer substrate 990, and the top electrode can have a length between half and one-quarter of the distance between positions 992 and 994 (and ends 907B and 908B). The formation of the shown portion of the top electrode 960B can be performed by, for example, sputtering deposition of a molybdenum layer. The molybdenum layer can then be patterned, etched, and cleaned to form the shown portion of the top electrode 960B, wherein the top electrode 960B extends no more than half of the distance between positions 992 and 994 (and ends 907B and 908B).

[0125] refer to Fig. 12A and Fig.12I, in operation 1216, portions of portion 990 between locations 992 and 994 may be removed to form structure 114 and opening 106. Removal of this portion of substrate 990 may be performed, for example, by a backside etching process operation. Additionally, bimorph tab 902B may be separated by an adjacent bimorph tab (e.g., bimorph tab 902A) by completely etching through at least respective portions of piezoelectric layers 980B and 982B proximate end 908B, thereby forming gap / slit 118.

[0126] Fig.13A and Fig. 13B A perspective view 1300 and a cross-sectional view 1350 of a portion of another example of a piezoelectric cantilever system 910 are provided, respectively. Fig.14A and Fig. 14B A perspective view 1400 and a cross-sectional view 1450 , respectively, of a portion of another example of a piezoelectric cantilever system 910 are provided. Fig.13A and Fig. 13B The example piezoelectric cantilever system 910 has a Fig. 9A and Fig. 9B The example piezoelectric cantilever system 910 in FIG. 1 has a similar electrode and piezoelectric layer arrangement, but the bottom electrode 964B is formed on the surface 1302 of the piezoelectric layer 982B, rather than being embedded in the piezoelectric layer 982B, so that the surface 1304 of the bottom electrode 964B and the surface 1302 of the piezoelectric layer 982B form a discontinuous surface. In addition, Fig.14A and Fig. 14B The example piezoelectric cantilever system 910 has a Fig.11A and Fig. 11B The example piezoelectric cantilever system 910 in FIG. 1 has a similar electrode and piezoelectric layer arrangement, but the bottom electrode 964B is formed on the surface 1400 of the piezoelectric layer 982B instead of being embedded in the piezoelectric layer 982B, so that the surface 1402 of the bottom electrode 964B and the surface 1400 of the piezoelectric layer 982B form a discontinuous surface. Fig.13A , Fig. 13B , Fig.14A and Fig. 14B The arrangement reduces discontinuities in the piezoelectric layer 982B, which can improve the reliability of the piezoelectric bimorph.

[0127] Fig.15A The manufacture of a piezoelectric cantilever system (such as Fig.13A , Fig. 13B , Fig.14A and Fig. 14B Flowchart of an example method 1500 of a piezoelectric cantilever system 910). In addition, Figure 15B-15E Shown in Fig.15A Piezoelectric cantilever system shown in various stages of fabrication.

[0128] refer to Fig.15A and Fig. 15B In operation 1502, a first electrode (e.g., bottom electrode 964B) is formed on an outer surface of a multilayer substrate (e.g., substrate 990), which may include an oxide layer and a semiconductor (e.g., silicon) substrate. The bottom electrode extends over position 992 to position 994 of the multilayer substrate 990, wherein positions 992 and 994 may correspond to, for example, ends 907B and 908B of a suspended portion of a piezoelectric bimorph fin 902B, respectively, which includes a bottom electrode formed in a subsequent operation. The bottom electrode may have a length between half and one-quarter of the distance between positions 992 and 994. The portion of the substrate 990 between positions 992 and 994 below the bottom electrode will be removed in a subsequent operation to form the opening 106 and the structure 114. For example, the formation of the shown portion of the bottom electrode 964B may be performed by sputtering a molybdenum layer on the substrate 990. The molybdenum layer may then be patterned, etched, and cleaned to form the illustrated portion of the bottom electrode 964B, wherein the bottom electrode 964B extends no more than half the distance between locations 992 and 994 (and ends 907B and 908B).

[0129] refer to Fig.15A and Fig. 15C In operation 1504, a sacrificial layer (eg, sacrificial layer 1565) is formed on the first electrode (eg, bottom electrode 964B) and corresponding portions of the substrate 990. The formation of the sacrificial layer 1065B as shown may be performed by, for example, sputtering deposition of an oxide layer.

[0130] refer to Fig.15A and Fig.15D In operation 1506, at least some of the sacrificial layer 1565 and / or the bottom electrode 964B can be removed to expose the bottom electrode 964B. In some examples, the sacrificial layer 1565 and / or the bottom electrode 964B can be subjected to a polishing operation, such as a chemical mechanical polishing (CMP) operation. As a result of the polishing operation, the bottom electrode 964B can be exposed, the remaining portion of the sacrificial layer 1565 is adjacent to the bottom electrode 964B, and the outer surface 1566 of the bottom electrode 964B and the outer surface 1567 of the sacrificial layer 1065B are substantially coplanar (or at least continuous).

[0131] refer to Fig.15A and Fig.15EIn operation 1508, a first piezoelectric layer (e.g., piezoelectric layer 982B) may be formed on the exposed portion of the bottom electrode 964B and the sacrificial layer 1565. Due to the planarization previously performed on the underlying layers, the piezoelectric layer 982B may have a substantially flat outer surface. This may improve the quality of the processing steps for each layer subsequently formed on the piezoelectric layer 982B.

[0132] Operation 1508 may be followed by, for example, operations 1006-1012 of method 1000 or operations 1206-1216 of method 1200 to form middle and top electrodes 960, 962, piezoelectric layer 980, and structure 114 and opening 106. Remaining portions of sacrificial layer 1565 may also be removed (e.g., by etching) before or after operations 1006-1012 or operations 1206-1216.

[0133] As used herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or the context indicates otherwise. Thus, as used herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or the context indicates otherwise. In addition, “and” is both joint and individual, unless expressly indicated otherwise or the context indicates otherwise. Thus, as used herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or the context indicates otherwise. To assist the Patent Office and any reader of any patent issued in this application in interpreting the appended claims, Applicant notes that, unless “means for” or “step for” are expressly used in the claim language, none of the appended claims is intended to invoke paragraph 6 of 35 U.S.C. § 112 as it exists on the filing date of this application.

[0134] In the foregoing description, for the purpose of explanation, many specific details are set forth to provide a thorough understanding of one or more examples. However, it is apparent to those of ordinary skill in the art that the present disclosure can be practiced without some or all of these specific details. In other cases, in order to avoid unnecessarily obscuring the present disclosure, well-known process steps or structures are not described in detail. In addition, although the present disclosure is described in conjunction with examples, the description is not intended to limit the present disclosure to the described examples. On the contrary, the description is intended to cover substitutions, modifications and equivalents that may be included in the spirit and scope of the present disclosure as defined by the appended claims.

[0135] In this specification, the term "coupled" may encompass connections, communications, or signal paths that achieve a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform an action: (a) in the first example, device A is coupled to device B through a direct connection; or (b) in the second example, if the intermediate component C does not change the functional relationship between device A and device B, device A is coupled to device B through the intermediate component C, so that device B is controlled by device A via the control signal generated by device A.

[0136] Additionally, in this specification, the recitation “based on” means “based at least in part on.” Thus, if X is based on Y, then X may be a function of Y and any number of other factors.

[0137] A device that is "configured to" perform a task or function may be configured (e.g., programmed and / or hardwired) by the manufacturer at the time of manufacture to perform the function, and / or may be configurable (or reconfigurable) by a user after manufacture to perform the function and / or other additional or alternative functions. The configuration may be programmable through the device's firmware and / or software, through the construction and / or layout of the device's hardware components and interconnections, or a combination thereof.

[0138] As used herein, the terms "terminal", "node", "interconnect", "pin" and "lead" are used interchangeably. Unless specifically stated to the contrary, these terms are generally used to refer to an interconnect or an end point between device elements, circuit elements, integrated circuits, devices or other electronic or semiconductor components.

[0139] Circuits or devices described herein that include certain components may be adapted to be coupled to these components to form the described circuit systems or devices. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and / or inductors), and / or one or more sources (such as voltage and / or current sources) may be adapted to include only semiconductor elements within a single physical device (e.g., a semiconductor die and / or an integrated circuit (IC) package) and may be adapted to be coupled to at least some of the passive elements and / or sources during or after manufacture (e.g., by an end user and / or a third party) to form the described structure.

[0140] The circuits described herein may be reconfigured to include additional or different components to provide functionality that is at least partially similar to functionality available prior to component replacement. Unless otherwise indicated, components shown as resistors generally represent any one or more elements coupled in series and / or in parallel to provide the amount of impedance represented by the resistors shown. For example, a resistor or capacitor shown and described herein as a single component may be replaced with a plurality of resistors or capacitors coupled in parallel between the same nodes, respectively. For example, a resistor or capacitor shown and described herein as a single component may be replaced with a plurality of resistors or capacitors coupled in series between the same two nodes as a single resistor or capacitor, respectively.

[0141] Although certain elements of the described examples may be included in an integrated circuit and other elements may be located outside the integrated circuit, in other example embodiments, more or fewer features may be incorporated into the integrated circuit. In addition, some or all of the features illustrated as external to the integrated circuit may be included in the integrated circuit, and / or some features illustrated as internal to the integrated circuit may be incorporated outside the integrated circuit. As used herein, the term "integrated circuit" means one or more circuits that: (i) are incorporated into / on a semiconductor substrate; (ii) are incorporated into a single semiconductor package; (iii) are incorporated into the same module; and / or (iv) are incorporated into / on the same printed circuit board.

[0142] In this specification, unless otherwise stated, “about”, “approximately” or “substantially” before a parameter means within + / - 10% of the parameter, or if the parameter is zero, within a reasonable value range around zero.

[0143] Modifications to the described embodiments are possible within the scope of the claims, and other embodiments are possible.

Claims

1. An audio device, comprising: a substrate having an opening; a first piezoelectric tab having a first end on the substrate and extending over a first portion of the opening, the first piezoelectric tab having a first terminal and a second terminal; a second piezoelectric tab having a second end on the substrate and extending over a second portion of the opening, the second piezoelectric tab being spaced apart from the first piezoelectric tab, the second piezoelectric tab having a third terminal and a fourth terminal; a transmitting circuit having a driver output; a first receiving circuit having a first receiver input; a switch circuit having a first switch terminal coupled to the driver output and the first receiver input and having a second switch terminal coupled to the first terminal and the second terminal; as well as The second receiving circuit has a second receiver input terminal coupled to the third terminal and the fourth terminal.

2. The audio device of claim 1, wherein the transmitting circuit is a first transmitting circuit, the driver output is a first driver output, and the switch circuit is a first switch circuit, the audio device further comprising: a second transmitting circuit having a second driver output terminal; as well as A second switch circuit has a third switch terminal and a fourth switch terminal, the third switch terminal being coupled to the second driver output and the second receiver input, and the fourth switch terminal being coupled to the third terminal and the fourth terminal.

3. The audio device according to claim 1, further comprising a control circuit coupled to the transmitting circuit and the first receiving circuit and the second receiving circuit, the control circuit being configured to: providing a drive signal to the first terminal and the second terminal through the transmitting circuit and the switching circuit, wherein the first piezoelectric flap is configured to vibrate in response to the drive signal; receiving a response signal from the second receiving circuit, the response signal indicating vibration of the second piezoelectric flap in response to the vibration of the first piezoelectric flap; generating a response spectrum based on the response signal; and Data representing the response spectrum is stored in a memory.

4. The audio device of claim 3, wherein the control circuit is further configured to: determining one or more measured frequency response characteristics from the response spectrum; comparing the one or more measured frequency response characteristics to one or more target frequency response characteristics; A status indication is provided based on a result of the comparison.

5. The audio device of claim 4, wherein the one or more measured frequency response characteristics include: Resonant frequency, lower cutoff frequency or quality factor.

6. An audio device according to claim 4, wherein the control circuit is configured to provide the status indication of at least one of the following: the presence of foreign matter on the first piezoelectric fin and the second piezoelectric fin, the presence of foreign matter in the rear volume space of the audio device, or the gap distance between the first piezoelectric fin and the second piezoelectric fin exceeds a threshold.

7. An audio device according to claim 6, wherein the drive signal is a first drive signal, and the control circuit is configured to provide a second drive signal to the first terminal and the second terminal through the transmitting circuit and the switching circuit in response to a status indication that a foreign object exists on the first piezoelectric fin and the second piezoelectric fin.

8. An audio device according to claim 6, wherein the foreign matter includes moisture, the audio device further includes a heater interfaced with the rear volume space, and the control circuit is configured to enable the heater in response to at least one of the following: the status indication of the presence of moisture on the first piezoelectric foil and the second piezoelectric foil, or the status indication of the presence of moisture in the rear volume space.

9. The audio device of claim 4, wherein the control circuit is configured to: determining an equalization coefficient based on the data; and An equalization operation is performed based on the equalization coefficients.

10. The audio device of claim 9, wherein the control circuit is configured to determine a resonant frequency and a lower cutoff frequency based on the data, determine a sensitivity of the second piezoelectric vane at the resonant frequency and the lower cutoff frequency based on the data, and determine the equalization coefficient based on the resonant frequency, the lower cutoff frequency, and the sensitivity.

11. The audio device of claim 2, further comprising a control circuit coupled to the transmitting circuit and the first receiving circuit and the second receiving circuit, the control circuit being configured to: in a first mode: providing a first drive signal to the first piezoelectric flap via the first transmitting circuit and the first switching circuit, wherein the first piezoelectric flap is configured to vibrate at a first resonant frequency in response to the first drive signal; and A second drive signal is provided to the second piezoelectric flap via the second transmitting circuit and the second switching circuit, wherein the second piezoelectric flap is configured to vibrate at a second resonant frequency in response to the second drive signal.

12. The audio device of claim 11 , wherein the control circuit is configured, in the second mode: receiving a first signal indicating detection of an audio signal from the first piezoelectric flap via the first receiving circuit and the first switching circuit; and A second signal representing detection of the audio signal is provided from the second piezoelectric flap via the second receiving circuit and the second switching circuit.

13. The audio device of claim 1, wherein: The first piezoelectric fin comprises: a first top electrode; a first bottom electrode; a first intermediate electrode having at least a portion between the first bottom electrode and the first top electrode; a first piezoelectric layer having at least a portion between the first top electrode and the first middle electrode; and a second piezoelectric layer having at least a portion between the first middle electrode and the first bottom electrode, the first top electrode and the first bottom electrode being coupled to the first terminal, and the first middle electrode being coupled to the second terminal; and The second piezoelectric fin comprises: a second top electrode; a second bottom electrode; a second intermediate electrode having at least a portion between the second top electrode and the second bottom electrode; a third piezoelectric layer having at least a portion between the second top electrode and the second middle electrode; and A fourth piezoelectric layer has at least a portion between the second middle electrode and the second bottom electrode, the second top electrode and the second bottom electrode are coupled to the third terminal, and the second middle electrode is coupled to the fourth terminal.

14. The audio device of claim 13, wherein: The first piezoelectric tab includes a first portion suspended above the first portion of the opening; at least one of the first top electrode, the first bottom electrode, or the first middle electrode extends no more than half of the first length of the first portion; The second piezoelectric tab includes a second portion suspended above the second portion of the opening; and At least one of the second top electrode, the second bottom electrode, or the second middle electrode extends no more than half of the second length of the second portion.

15. The audio device of claim 14, wherein the at least one of the first top electrode, the first bottom electrode, or the first middle electrode extends between one quarter of the first length and one half of the first length; and Wherein the at least one of the second top electrode, the second bottom electrode or the second middle electrode extends between one quarter of the second length and one half of the second length.

16. The audio device of claim 14, wherein the first piezoelectric layer extends no more than half of the first length of the first portion, and the second piezoelectric layer extends no more than half of the second length of the second portion.

17. The audio device of claim 14, wherein the first bottom electrode is embedded in the first piezoelectric layer, and a first surface of the first bottom electrode is continuous with a second surface of the first piezoelectric layer; and The second bottom electrode is embedded in the second piezoelectric layer, and a third surface of the second bottom electrode is continuous with a fourth surface of the second piezoelectric layer.

18. The audio device of claim 14, wherein the first bottom electrode is on a first surface of the second piezoelectric layer, the first surface and a second surface of the first bottom electrode being discontinuous; and The second bottom electrode is on the third surface of the fourth piezoelectric layer, and the third surface and the fourth surface of the second bottom electrode are discontinuous.

19. A method comprising: driving a first piezoelectric flap of the audio device with a first electrical signal to generate an acoustic signal; receiving a second electrical signal from a second piezoelectric flap of the audio device in response to the acoustic signal; determining a characteristic of the audio device based on the second electrical signal; as well as An action is performed based on the characteristic.

20. The method of claim 19, wherein the characteristic comprises at least one of: the presence of foreign matter on the first piezoelectric fin and the second piezoelectric fin, the presence of foreign matter in the rear volume space of the audio device, or the gap distance between the first piezoelectric fin and the second piezoelectric fin exceeds a threshold.

21. The method of claim 19, wherein the actions include: The first piezoelectric foil is driven at a first resonant frequency of the first piezoelectric foil, and the second piezoelectric foil is driven at a second resonant frequency of the second piezoelectric foil.

22. The method of claim 19, wherein the action comprises activating a heater of the audio device.

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