Micromachining ultrasonic transducers with both out-of-plane and in-plane actuation and displacement

Abstract

This document provides a capacitive transducer (200). The capacitive transducer (200) includes: a plate (202) including a protruding central mass block (203); and a substrate (204) having a central recess (205) configured to receive the central mass block (203). The capacitive transducer (200) also includes a first electrode (210) coupled to a non-horizontal edge surface of the central mass block (203) and a second electrode (211) coupled to a non-horizontal edge surface of the central recess (205). The capacitive transducer (200) also includes a third electrode (216) coupled to a horizontal edge surface of the central mass block (203) and a fourth electrode (218) coupled to a horizontal edge surface of the central recess (205). The plate (202) is coupled to the substrate (204) at least along the outer peripheral region of the plate (202) and the substrate (204).

Description

Background Technology

[0001] The subject matter disclosed herein relates to transducers, and more specifically to micromachining ultrasonic transducers with both out-of-plane and in-plane actuation and displacement.

[0002] Ultrasound equipment can be used to image targets such as organs and soft tissues in the human body, as well as non-human targets. For example, in addition to ultrasound imaging of humans and animals, ultrasound equipment can also be used for applications such as ultrasound / acoustic sensing, non-destructive evaluation (NDE), and ultrasound therapy (e.g., high-intensity focused ultrasound (HIFU)).

[0003] Ultrasonic equipment can use real-time, non-invasive high-frequency sound waves to generate a series of two-dimensional (2D) and / or three-dimensional (3D) images. Sound waves can be emitted by a transmitting transducer, and the reflection of the emitted sound waves can be received by a receiving transducer. The received sound waves can then be processed to display an image of the target. Conventional capacitive micromachining ultrasonic transducers (CMUTs) used as transmitting and / or receiving transducers may include a top electrode and a bottom electrode, wherein the top electrode can move due to an electrical signal used to generate the sound waves, or due to receiving sound waves used to generate a processable electrical signal. The top and bottom electrodes may be separated by a gap, which may include a degree of vacuum or be filled with, for example, air. However, conventional and traditional CMUTs may have certain limitations or disadvantages. Summary of the Invention

[0004] The following outlines some embodiments commensurate with the scope of the originally claimed subject matter. These embodiments are not intended to limit the scope of the claimed subject matter, but rather to provide only a brief overview of the possible forms of the subject matter. In reality, the subject matter may include many forms that may be similar to or different from the embodiments described below.

[0005] According to a first embodiment, a capacitive transducer is provided. The capacitive transducer includes: a plate including a protruding central mass block; and a substrate having a central recess configured to receive the central mass block. The capacitive transducer includes a first electrode coupled to a non-horizontal edge surface of the central mass block and a second electrode coupled to a non-horizontal edge surface of the central recess. The capacitive transducer further includes a third electrode coupled to a horizontal edge surface of the central mass block and a fourth electrode coupled to a horizontal edge surface of the central recess. The plate is coupled to the substrate at least along the outer peripheral region of the plate and the substrate.

[0006] According to a second embodiment, a system is provided. The system includes a capacitive transducer. The capacitive transducer includes: a plate including a protruding central mass block; and a substrate having a central recess configured to receive the central mass block. The capacitive transducer also includes a first pair of electrodes disposed on a non-horizontal surface of the capacitive transducer and a second pair of electrodes disposed on a horizontal surface of the capacitive transducer. The system also includes circuitry configured to actuate the capacitive transducer by applying a direct current (DC) signal to the first pair of electrodes and an alternating current (AC) signal to the second pair of electrodes.

[0007] According to a third embodiment, a capacitive transducer is provided. The capacitive transducer includes: a plate including a protruding central mass block; and a substrate having a central recess configured to receive the central mass block. The capacitive transducer further includes a first electrode coupled to a non-horizontal edge surface of the central mass block and a second electrode coupled to a non-horizontal edge surface of the central recess. The capacitive transducer also includes a third electrode coupled to a horizontal edge surface of the central mass block and a fourth electrode coupled to a horizontal edge surface of the central recess. The capacitive transducer further includes a first insulating layer disposed on a portion of the third electrode, a second insulating layer disposed on a portion of the fourth electrode, or both a first insulating layer disposed on a portion of the third electrode and a second insulating layer disposed on a portion of the fourth electrode. Attached Figure Description

[0008] These and other features, aspects, and advantages of the invention will be better understood when reading the following detailed description with reference to the accompanying drawings, in which the same reference numerals denote the same parts throughout the drawings, wherein:

[0009] Figure 1 This is a block diagram of an exemplary ultrasound system that can be used for ultrasound imaging according to various implementation schemes;

[0010] Figure 2A and Figure 2B A cross-section of an exemplary capacitive micromachining ultrasonic transducer (CMUT) configuration with dual out-of-plane and in-plane actuation and displacement is shown according to various embodiments.

[0011] Figure 3 Exemplary applicable dimensions of the exemplary CMUT shown in Figure 2 according to various embodiments are illustrated;

[0012] Figure 4 An exemplary applicable size for another CMUT according to various implementation schemes is shown;

[0013] Figure 5Another configuration of an exemplary CMUT with dual out-of-plane and in-plane actuation and displacement is shown according to various embodiments;

[0014] Figure 6 Another configuration of an exemplary CMUT with dual out-of-plane and in-plane actuation and displacement is shown according to various embodiments;

[0015] Figure 7 Another configuration of an exemplary CMUT with dual out-of-plane and in-plane actuation and displacement is shown according to various embodiments;

[0016] Figure 8 Another configuration of an exemplary CMUT with dual out-of-plane and in-plane actuation and displacement is shown according to various embodiments;

[0017] Figure 9 The comparisons during edge mode activation and dual mode activation according to various implementation schemes are shown. Figure 4 Example bandwidth curve of CMUT;

[0018] Figure 10 A series of exemplary graphs are shown comparing the effects of in-plane electrode coverage on pressure and bandwidth of an exemplary CMUT during dual-mode activation according to various implementations;

[0019] Figure 11 Exemplary graphs comparing the effects of in-plane electrode coverage on pressure and bandwidth of an exemplary CMUT during dual-mode activation, according to various embodiments, are shown; and

[0020] Figure 12 and Figure 13 A schematic diagram illustrating the manufacture of an exemplary CMUT with biplane out-of-plane and in-plane actuation and displacement according to various embodiments is shown. Detailed Implementation

[0021] One or more specific implementations will be described below. To provide a concise description of these implementations, not all characteristics of the actual implementation may be described in this specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developer's specific objectives, such as complying with system-related and business-related constraints that may differ from implementation to implementation. Furthermore, it should be understood that such development efforts may be complex and time-consuming, but remain routine tasks of design, fabrication, and manufacturing for those skilled in the art who benefit from this disclosure.

[0022] When describing elements of various embodiments of the subject matter of this invention, the articles “a,” “an,” “the,” and “the” are intended to indicate the presence of one or more of the stated elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that additional elements may be present in addition to the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and therefore the additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.

[0023] The embodiments contemplated by this invention provide a micromachining ultrasonic transducer (e.g., a CMUT) with both out-of-plane and in-plane actuation and displacement. Specifically, a direct current (DC) signal or bias can be applied to a pair of vertical electrodes (e.g., for out-of-plane actuation) and an alternating current (AC) signal can be applied to a pair of horizontal electrodes (e.g., for in-plane actuation). Actuation with a DC signal is orthogonal to the displacement direction of the central mass block of the plate toward the recess of the substrate, while actuation with an AC signal is parallel to the displacement direction. In-plane actuation with an AC signal increases the electromechanical coupling factor. This allows the CMUT to have a higher transmit bandwidth when a DC signal is applied to a pair of vertical electrodes and when an AC signal is applied to a pair of horizontal or in-plane electrodes, which is entirely different from when both AC and DC signals are applied to the pair of vertical electrodes. The disclosed CMUT can operate in both a conventional operating mode and a mechanical collapse operating mode (e.g., when the central mass block of the plate contacts the substrate). Furthermore, the disclosed CMUT can operate with different drive configurations. For example, during operation in transmit mode, only an AC signal can be applied to a pair of horizontal electrodes, while no DC bias or AC current signal is applied to a pair of vertical electrodes. Furthermore, during operation in transmit and receive modes, a DC signal can be applied to either a pair of vertical electrodes or a pair of horizontal electrodes. For instance, during the transmit portion of transmit and receive modes, a DC signal can be applied to a pair of vertical electrodes and an AC signal can be applied to a pair of horizontal electrodes; similarly, during the receive portion of transmit and receive modes, both AC and DC signals can be applied to a pair of horizontal electrodes.

[0024] While CMUT can be used for medical imaging, it can also be used for a variety of other purposes besides ultrasound imaging of humans or animals, such as ultrasound / acoustic sensing, non-destructive evaluation (NDE), ultrasound therapy (e.g., high-intensity focused ultrasound (HIFU)), etc.

[0025] As used herein, the term “image” broadly refers to both a visual image and the data representing that image. However, many implementations generate (or are configured to generate) at least one visual image. Furthermore, as used herein, the phrase “image” is used to refer to ultrasound modes such as B-mode (2D mode), M-mode, three-dimensional (3D) mode, CF mode, PW Doppler, CW Doppler, MGD, and / or submodes of B-mode and / or CF such as shear wave elastography (SWEI), TVI, Angio, B-flow, BMI, BMI_Angio, and in some cases also MM, CM, TVD, where “image” and / or “plane” includes a single beam or multiple beams.

[0026] Furthermore, as used herein, the term processor or processing unit refers to any type of processing unit capable of performing the required computations required for various implementation schemes, such as single-core or multi-core: CPU, Accelerated Processing Unit (APU), graphics board, DSP, FPGA, ASIC, or combinations thereof.

[0027] Figure 1 This is a block diagram of an exemplary ultrasound system that can be used for ultrasound imaging according to various embodiments. Reference Figure 1 A block diagram of an exemplary ultrasound system 100 is shown. The ultrasound system 100 includes a transmitter 102, an ultrasound probe 104, a transmit beamformer 110, a receiver 118, a receive beamformer 120, an A / D converter 122, an RF processor 124, an RF / IQ buffer 126, a user input device 130, a signal processor 132, an image buffer 136, a display system 134, and a file 138. Circuit 111 is a typical example of cMUT bias, but many options are described in public literature.

[0028] Transmitter 102 may include suitable logic, circuitry, interfaces, and / or code operable to drive ultrasound probe 104. Ultrasound probe 104 may include, for example, a single element CMUT, a 1D array of CMUTs, a 2D array of CMUTs, a ring (loop) array of CMUTs, etc. Therefore, ultrasound probe 104 may include a group of transducer elements 106, which may be, for example, CMUTs. In some embodiments, ultrasound probe 104 is operable to acquire ultrasound image data covering at least a majority of, for example, anatomical structures (such as the heart, blood vessels, or any suitable anatomical structure). Each transducer element in transducer element 106 may be referred to as a channel.

[0029] The transmit beamformer 110 may include suitable logic, circuitry, interfaces, and / or code operable to control the transmitter 102, which drives the set of transmit transducer elements 106 to transmit ultrasonic signals to a region of interest (e.g., a person, animal, underground cavity, physical structure, etc.). The transmitted ultrasonic signals may be backscattered from structures (such as blood cells or tissue) within the object of interest to generate echoes. The transducer elements 106 may then receive the echoes. For example, one or more drive circuits 111 may be coupled to and drive or control the electrodes of each transducer element 106. For example, one or more drive circuits may be coupled to separate AC and DC voltage sources.

[0030] The set of transducer elements 106 in the ultrasonic probe 104 is operable to convert the received echo into an analog signal and transmit it to a receiver 118. The receiver 118 may include suitable logic, circuitry, interfaces, and / or code operable to receive the signal from the ultrasonic probe 104. The analog signal can be transmitted to one or more of a plurality of A / D converters 122.

[0031] Therefore, the ultrasound system 100 can be multiplexed, allowing ultrasound transmission signals to be emitted during specific time periods and echoes of these signals to be received during other time periods. Although not explicitly shown, various embodiments of this disclosure can allow the transmission of ultrasound signals and the reception of echoes from these signals to occur simultaneously. In such cases, the probe may include transmitting transducer elements and receiving transducer elements.

[0032] Multiple A / D converters 122 may include suitable logic, circuitry, interfaces, and / or code operable to convert analog signals from receiver 118 into corresponding digital signals. The multiple A / D converters 122 are disposed between receiver 118 and RF processor 124. However, this disclosure is not limited in this respect. Therefore, in some embodiments, multiple A / D converters 122 may be integrated within receiver 118.

[0033] RF processor 124 may include suitable logic, circuitry, interfaces, and / or code operable to demodulate digital signals output from a plurality of A / D converters 122. According to one embodiment, RF processor 124 may include a demodulator (not shown) operable to demodulate digital signals to form I / Q data pairs representing corresponding echo signals. RF data (which may be, for example, I / Q signal data, real-valued RF data, etc.) can then be transmitted to RF / IQ buffer 126. RF / IQ buffer 126 may include suitable logic, circuitry, interfaces, and / or code operable to provide temporary storage of RF or I / Q signal data generated by RF processor 124.

[0034] Therefore, various implementations enable, for example, RF processor 124 to process real-valued RF data or any other equivalent representation of such data with a suitable RF buffer 126.

[0035] The receive beamformer 120 may include suitable logic, circuitry, interfaces, and / or code operable to perform digital beamforming processing to, for example, sum the delayed channel signal, phase-shifted channel signal, and / or weighted channel signal received from the RF processor 124 via the RF / IQ buffer 126 and output a beam summation signal. The delayed channel data, phase-shifted channel data, and / or weighted channel data may be summed to form scan lines output from the receive beamformer 120, wherein the scan lines may be, for example, complex-valued or non-complex-valued. A specific delay of the channel may be provided, for example, by the RF processor 124 or any other processor configured to perform this task. The delayed channel data, phase-shifted channel data, and / or weighted channel data may be referred to as delay-aligned channel data.

[0036] The processed information obtained can be a beam summation signal output from the receiving beamformer 120 and transmitted to the signal processor 132. According to some embodiments, the receiver 118, multiple A / D converters 122, RF processor 124, and beamformer 120 can be integrated into a single beamformer, which can be digital. In various embodiments, the ultrasound system 100 may include multiple receiving beamformers 120.

[0037] User input device 130 can be used to input patient data, scan parameters, settings, select protocols and / or templates, etc. In an exemplary embodiment, user input device 130 is operable to configure, manage and / or control the operation of one or more components and / or modules in ultrasound system 100. In this regard, user input device 130 can be used to configure, manage and / or control the operation of transmitter 102, ultrasound probe 104, transmit beamformer 110, receiver 118, receive beamformer 120, RF processor 124, RF / IQ buffer 126, user input device 130, signal processor 132, image buffer 136, display system 134 and / or file 138. User input device 130 may include switches, buttons, rotary encoders, touch screens, motion tracking, voice recognition, mouse devices, keyboards, cameras and / or any other devices capable of receiving user guidance. In some embodiments, for example, one or more user input devices in user input device 130 may be integrated into other components, such as display system 134 or ultrasound probe 104. For example, user input device 130 may include a touchscreen display.

[0038] Signal processor 132 may include suitable logic, circuitry, interfaces, and / or code operable to process ultrasound scan data (i.e., summed IQ signals) to generate an ultrasound image for presentation on display system 134. Signal processor 132 is operable to perform one or more processing operations based on multiple selectable ultrasound modalities on the acquired ultrasound scan data. In exemplary embodiments, signal processor 132 may be used to perform display processing and / or control processing, etc. Acquired ultrasound scan data can be processed in real time during a scanning session as echo signals are received. Additionally or alternatively, ultrasound scan data may be temporarily stored in RF / IQ buffer 126 during a scanning session and processed in online or offline operation. In various embodiments, processed image data may be presented at display system 134 and / or stored at archive 138. Archive 138 may be a local archive, a Picture Archiving and Communication System (PACS), or any suitable device for storing images and related information.

[0039] Signal processor 132 may include one or more central processing units, microprocessors, microcontrollers, etc. For example, signal processor 132 may be an integrated component or may be distributed across various locations. In exemplary embodiments, signal processor 132 may be able to receive input information from user input device 130 and / or file 138, generate output that can be displayed by display system 134, and manipulate the output in response to input information from user input device 130, etc. Signal processor 132 may be able to perform, for example, any of the methods and / or instruction sets discussed herein according to various embodiments.

[0040] The ultrasound system 100 is operable to continuously acquire ultrasound scan data at a frame rate suitable for the imaging situation under consideration. Typical frame rates range from 20 to 120, but can be lower or higher. The acquired ultrasound scan data can be displayed on the display system 134 at the same, slower, or faster frame rate. An image buffer 136 is included for storing frames of acquired ultrasound scan data that are not scheduled for immediate display. Preferably, the image buffer 136 has sufficient capacity to store frames of ultrasound scan data for at least several minutes. Frames of ultrasound scan data are stored in a manner that facilitates retrieval based on their acquisition order or time. The image buffer 136 can be embodied in any known data storage medium.

[0041] Display system 134 can be any device capable of transmitting visual information to a user. For example, display system 134 may include a liquid crystal display, a light-emitting diode display, and / or any suitable one or more displays. Display system 134 may be operable to present ultrasound images and / or any suitable information.

[0042] File 138 may be one or more computer-readable storage devices integrated with and / or communicatively coupled (e.g., via a network) to ultrasound system 100, such as Image Archiving and Communication System (PACS), server, hard disk, floppy disk, CD, CD-ROM, DVD, compact memory, flash memory, random access memory, read-only memory, electrically erasable and programmable read-only memory, and / or any suitable memory. File 138 may include, for example, a database, library, information set, or other memory accessed by and / or incorporated into signal processor 132. For example, file 138 may be able to temporarily or permanently store data. File 138 may be able to store medical image data, data generated by signal processor 132, and / or instructions readable by signal processor 132, etc.

[0043] The components of the ultrasound system 100 can be implemented in software, hardware, firmware, etc. The various components of the ultrasound system 100 can be communicatively connected. The components of the ultrasound system 100 can be implemented individually and / or integrated in various forms. For example, the display system 134 and the user input device 130 can be integrated as a touchscreen display. Furthermore, although the ultrasound system 100 is described as including a receive beamformer 120, an RF processor 124, and a signal processor 132, various embodiments of this disclosure may use various numbers of processors. For example, various devices that execute code may generally be referred to as processors. Various embodiments may refer to each of these devices, including each of the RF processor 124 and the signal processor 132, as a processor. In addition, there may be other processors to additionally perform tasks described as being performed by these devices including the receive beamformer 120, the RF processor 124, and the signal processor 132, and for ease of description, all of these processors may be referred to as "processors".

[0044] A typical CMUT consists of two plates separated by a vacuum or fluid gap. The plates are biased with a DC voltage and then superimposed with an AC signal of selected frequency and amplitude. The CMUT operates based on Coulomb's law of attraction. During DC bias, electrostatic and mechanical restoring forces balance each other, holding the membrane in the target displacement position. However, at a certain DC bias voltage, the electrostatic force exceeds the restoring force, and the membrane contacts the bottom electrode. For a fully clamped CMUT plate, this physical phenomenon occurs at approximately one-third of the effective gap height. This distance is called the pull-in or collapse distance, and the voltage at which this phenomenon occurs is called the collapse or pull-in voltage. Operating the device in collapse mode provides a higher level of acoustic power and a wider bandwidth during operation. One or more insulating layers may be sandwiched between the active membrane (top electrode), the gap (vacuum or fluid), and the back support structure (with the bottom electrode) to prevent short circuits during such collapse phenomena.

[0045] Collapse voltage V col The formulas are shown in Formulas 1 and 2 below (example of a flat rigid concentrator model):

[0046]

[0047] Where K is the membrane stiffness, ε0 is the dielectric constant of free space, and A is the device area. The effective gap height is given by the following formula:

[0048]

[0049] Where g0 is the vacuum / air gap, t i It is the thickness of the insulation layer, and ε i It is the dielectric constant of the insulating layer material.

[0050] In the following figures, it should be noted that the terms vertical and horizontal are defined relative to the longitudinal axis or length of the CMUT device (e.g., extending in the X direction). Therefore, the vertical direction will be orthogonal to the longitudinal axis or length of the CMUT device, and the horizontal direction will be parallel to the longitudinal axis or length of the CMUT device.

[0051] Figure 2A A cross-section of an exemplary CMUT configuration with biplane out-of-plane and in-plane actuation and displacement according to various embodiments is shown. Referring to FIG2, a CMUT 200 including a plate 202 and a substrate 204 is shown. The plate 202 may include a central mass block 203. The central mass block 203 protrudes downward into a recess 205 in a corresponding region of the substrate 204. The substantially vertical edge (or non-horizontal edge) of the central mass block 203 includes an electrode 210, and the substantially vertical edge of the recess 205 includes an electrode 211. The bottom surface 212 of the central mass block 203 faces the top surface 214 of the recess 205. The substantially horizontal edge of the bottom surface 212 includes an electrode 216, and the substantially horizontal edge of the top surface 214 includes an electrode 218. Although not shown, the electrodes 216, 218 may have a circular shape (as shown in the figure) when viewed from above in the XY plane. Figure 7 and Figure 8The electrodes 210, 211, 216, 218 are shown in rectangular or any other shape. Electrical signals (DC bias and AC signal) for moving plate 202 in the Z direction to generate sound waves can be provided to electrodes 210, 211 and 216, 218. The CMUT 200 can operate in transmit mode (Tx), receive mode (Rx), and / or transmit and receive (Tx-Rx) mode. Additionally, the CMUT 200 can operate in a normal mode or a mechanical collapse mode (e.g., when bottom surface 212 contacts top surface 214 of recess 205). Different drive configurations can be used for the CMUT 200. For example, a DC bias can be applied to electrodes 210, 211 (edge ​​electrodes) or electrodes 216, 218 (in-plane electrodes or center electrodes). For example, during the operation of the CMUT 200 in Tx-Rx mode, a DC bias signal is applied to electrodes 210 and 211, and during the transmit phase, only an AC signal is applied to electrodes 216 and 218. During the receive phase, both the DC bias signal and the AC signal are applied to electrodes 210 and 211. In this configuration, different DC voltage levels can be applied to the corresponding electrode pairs (electrodes 210, 211 and 216, 218) during transmit, receive, or transmit and receive. During the operation of the CMUT 200 in Tx mode, only the AC signal can be applied to electrodes 216, 218, and no DC signal is applied to either electrode pair (electrodes 210, 211 and 216, 218). In this scenario, the CMUT 200 can be driven at half the target frequency to receive harmonics at the output. In Rx mode, both the DC bias signal and the AC signal are applied to electrodes 210 and 211.

[0052] One or more insulating layers or bumps or high contact resistance layers or bumps may be sandwiched between electrodes 216, 218 in the event of mechanical collapse or accidental contact to prevent short circuits. As depicted, an insulating layer or bump 220 (or a high contact resistance layer or bump) is disposed on a portion of electrode 216, and an insulating layer or bump 222 (or a high contact resistance layer or bump) is disposed on a portion of electrode 218. In some embodiments, only the insulating layer or bump 220 (or the high contact resistance layer or bump) is disposed on electrode 216. In other embodiments, only the insulating layer or bump 222 (or the high contact resistance layer or bump) is disposed on electrode 218.

[0053] The plate 202 may be coupled to the substrate 204 at the outer peripheral region 202A of the plate 202. The coupling may be performed by any suitable method, including processes known in MEMS manufacturing, such as wafer bonding.

[0054] As can be seen, the CMUT 200 has an upper vertical gap 206A and a lower vertical gap 206B between the plate 202 and the substrate 204. A horizontal gap 208 also exists between electrodes 210 and 211. Furthermore, a vertical gap 224 (and corresponding insulating layers 220 and 222 or high contact resistance layers) exists between electrodes 216 and 218. The horizontal gap 208 and the vertical gap 224 can be referred to as electrode gap 208 and electrode gap 224. When a DC bias is applied to electrodes 210 and 211 and an AC signal is applied to electrodes 216 and 218 (i.e., dual-mode actuation), the vertical gaps 206A and 206B are the actuation boundaries that make the AC signal parallel to the device displacement direction along the Z-axis and make the DC bias orthogonal to the device displacement direction along the Z-axis. When both a DC bias and an AC signal are applied to the electrodes (i.e., edge mode activation), the vertical gaps 206A and 206B act as actuation boundaries that make the DC bias and AC signal orthogonal to the device displacement direction along the Z-axis. Operation in dual-mode actuation improves electromechanical coupling compared to edge mode operation. Although not shown, the CMUT200 can have a circular, rectangular, or any other shape when viewed from above in the XY plane.

[0055] Because the CMUT plate 202 is mechanically constrained in the X direction due to clamping at its edge (outer peripheral region 202A of the plate 202), the displacement degree of freedom can be primarily in the Z direction. Therefore, even if actuation is in the X direction (e.g., during edge-mode actuation and in dual-mode actuation via DC bias), the X-direction displacement can be much smaller than the Z-direction displacement due to the mechanical constraint. Various embodiments of this disclosure may have a displacement ratio of, for example, 10 or greater, regarding the relationship between Z-direction and X-direction displacements. It can be noted that the displacement ratio can be determined for the specific application of the CMUT 200. Figure 2B An alternative embodiment of the CMUT with a large outer peripheral area 202A is shown, wherein the plate 202 is coupled to the substrate 204.

[0056] Figure 3 Exemplary applicable dimensions of the exemplary CMUT shown in Figure 2 according to various embodiments are illustrated. Reference Figure 3 This shows a partial view of CMUT 300, which can be similar to CMUT 200. Dimensions may include, for example, the plate radius (P). r 302. Mass radius (M) r 304. Horizontal clearance (G) h 306. Vertical clearance (G) v )307 and 309, mass thickness (M) t 305. Plate thickness (P) t 303. In-plane electrode radius (Eip) RThe horizontal gap 306 and the vertical gap 309 may be referred to as electrode gap 306 and electrode gap 309, respectively. The vertical gap 309 is defined as the gap between any insulating layers (e.g., insulating layers 220 and / or 222) disposed on and between in-plane electrodes (e.g., electrodes 216 and 218 in FIG. 2).

[0057] Vertical clearance (G) v 307 and 309 can be equal to each other. Vertical clearance (G) v 307 and / or 309 can be equal to the horizontal clearance (G) h 306. Vertical clearance (G) v )307 and / or 309 may be greater than or less than the horizontal clearance (G h 306. Various gaps can be measured in any appropriate unit such as micrometers, nanometers, etc.

[0058] Term "E" PI "It can be the electrical pull-in voltage, or the DC bias required to cause the electrodes to collapse toward each other in the X direction. The term 'E'..." MC "The voltage required for mechanical collapse. Mechanical collapse is defined as the phenomenon that occurs when the central mass block 203 contacts the bottom of the recess 205 of the substrate 204 under a certain DC bias."

[0059] Due to the differences in the above parameters, E MC The implementation can vary. For example, the CMUT300 can have the following dimensions: 50 μM P r P r / 3 of M r 300nm P t 2*G v M t 100nm G v 0.2*G v G h These sizes can achieve an E of 34 volts (V). MC Increase the plate radius P r With mass radius M r The ratio can lead to (e.g., to P) r / M r For 2)E MC Increase (e.g., to 36V). Decrease plate radius P r With mass radius M r The ratio can lead to (e.g., to P) r / M r (4)E MC Reduce (e.g., to 30V). Eliminate vertical gap 307 (e.g., between plate 202 and substrate 204, such as...). Figure 4 As described in CMUT 350, it can significantly increase E MC (For example, up to 182V). E MC It can also vary depending on the material used in different layers.

[0060] Figure 5 Another configuration of an exemplary CMUT with both out-of-plane and in-plane actuation and displacement, according to various embodiments, is shown. References Figure 5 The diagram illustrates CMUT 500, which is similar to CMUT 200, except that the edges of the central mass block 503 of plate 502 and the recess 505 of substrate 504 are diagonally aligned. Therefore, the orientations of electrodes 506 and 507 are also diagonally aligned. These diagonal edges can also be referred to as non-horizontal edges, where the tilt angle (θ) is greater than 0 degrees (e.g., conventional equipment) and less than 90 degrees (e.g., edge equipment). The orthogonal distance between electrodes 506 and 507 can be referred to as the electrode gap 508. Similar to CMUT 200, CMUT 500 includes horizontal or in-plane electrodes 510 and 512 and corresponding insulating layers 514 and 516.

[0061] Figure 6 Another configuration of an exemplary CMUT with both out-of-plane and in-plane actuation and displacement, according to various embodiments, is shown. References Figure 6 The diagram illustrates CMUT 600, which is similar to CMUT 200, except that the edges of the central mass block 603 and the recess 605 are corrugated. Therefore, electrodes 606 and 607 are horizontally offset from electrodes 608 and 609. A horizontal gap 610 exists between electrodes 606 and 607 and between electrodes 608 and 609. The corrugated edges can also be referred to as non-horizontal edges. The horizontal gap 610 can be referred to as electrode gap 610. Similar to CMUT 200, CMUT 600 includes horizontal electrodes or in-plane electrodes 612 and 614 and corresponding insulating layers 616 and 618.

[0062] Figure 7 Another configuration of an exemplary CMUT with both out-of-plane and in-plane actuation and displacement, according to various embodiments, is shown. References Figure 7 The diagram shows a top cross-sectional view (e.g., XY plane) of the CMUT 1300 including in-plane actuation electrode 1301, illustrating the pattern of the horizontal gap 1310. Side cross-sectional views (e.g., XZ plane) 1302 and 1304 are also shown, illustrating the horizontal gap 1312 between electrodes (e.g., vertical or edge electrodes), and upper vertical gap 1314 and lower vertical gap 1316 (e.g., between in-plane or horizontal electrodes). The horizontal gap 1312 may be similar to... Figure 3The horizontal gap is 306. The upper vertical gap is 1314, which can be similar to... Figure 3 The upper vertical gap 307 and the lower vertical gap 1316 can be similar to Figure 3 The lower vertical gap 309 is shown. It can be seen that sectional view 1302 is directed at the outer portion of the horizontal gap 1310, and sectional view 1304 is directed at the inner portion of the horizontal gap 1310.

[0063] Figure 8 Another configuration of an exemplary CMUT with both out-of-plane and in-plane actuation and displacement, according to various embodiments, is shown. References Figure 8 The diagram shows a top cross-sectional view (e.g., XY plane) of the CMUT 1400 including in-plane actuation electrode 1401, illustrating the pattern of the horizontal gap 1410. Side cross-sectional views (e.g., XZ plane) 1402 and 1404 are also shown, illustrating the horizontal gap 1412 between electrodes (e.g., vertical or edge electrodes) and a lower vertical gap 1416 (e.g., between in-plane or horizontal electrodes). The horizontal gap 1412 may be similar to... Figure 3 The horizontal gap is 306. The lower vertical gap is 1416, which can be similar to... Figure 3 The lower vertical gap 309 is shown. It can be seen that sectional view 1402 is directed at the outer portion of the horizontal gap 1410, and sectional view 1404 is directed at the inner portion of the horizontal gap 1410.

[0064] While two exemplary configurations for increasing the total surface area of ​​the electrodes in horizontal gaps 1310 and 1410, which can be used in CMUT 1300 and CMUT 1400 respectively, are shown, the horizontal gaps can be any of a variety of shapes when viewed from above (e.g., the XY plane), such as circles, ellipses, regular polygons, or irregular polygons. The horizontal gaps can be continuous, such as... Figure 7 and Figure 8 The diagram shows one or more discrete parts that do not completely surround the CMUT, or one or more discrete parts that surround the CMUT together. Therefore, when viewed from above (e.g., the XY plane), the horizontal gaps of the CMUT may include one or more gaps, where each gap can be any geometry with any pattern.

[0065] Furthermore, any CMUT can have any geometry when viewed from above (e.g., the XY plane). For example, while CMUT 1300 and CMUT 1400 are shown as circular, a CMUT can be elliptical, oval, polygonal, etc. Additionally, although several configurations are shown, various embodiments of this disclosure are not necessarily limited to these. For example, CMUT 200 can have multiple electrodes 210 and 211, similar to CMUT 600. That is, while the edges can be planar, multiple electrodes can be present, which can be multiple electrodes 210 and corresponding multiple electrodes 211. Alternatively, a different number of electrodes 210 than electrodes 211 can be present, where, for example, multiple electrodes 210 can be used for a single electrode 211, or vice versa.

[0066] Furthermore, the central mass blocks 203, 503, 603, etc., may have shapes different from those disclosed in the examples. For example, the central mass block 503 may have rounded (convex) edges, and the recess 505 of the base 504 may have rounded (convex) edges, such that the recess 505 can receive the central mass block 503. Therefore, various embodiments of this disclosure may have appropriately rounded electrodes 506 and 507.

[0067] However, the shape of the central mass block and / or the recess of the substrate need not be limited to those mentioned in this disclosure. Rather, any suitable shape may be used. Furthermore, the electrodes placed on the edge surfaces of the central mass block and / or the recess may have a shape that conforms to the edge surfaces or a shape that differs from the edge surfaces.

[0068] Furthermore, although edges, surfaces, and electrodes are described in various ways, an edge, surface, or electrode can be a single, continuous edge / surface / electrode. For example, when the central mass block 203 is cylindrical, it may include a single vertical surface. Therefore, the CMUT 200 may have a single electrode 210 and a single electrode 211. However, even in the presence of a single surface, multiple electrodes 210 and multiple electrodes 211 may be placed at regular intervals along the single surface of the central mass block 203 of the plate 202 and / or the single surface of the recess 205 of the substrate 204.

[0069] Furthermore, the gaps described in the various figures may be filled with a fluid such as air, or may include a certain level of vacuum. Therefore, in various embodiments of this disclosure, the capacitive transducer may be configured such that the gap is airtight.

[0070] Figure 9 The comparisons during edge mode activation and dual mode activation according to various implementation schemes are shown. Figure 4 An exemplary bandwidth graph for the CMUT 350. (Reference) Figure 9, shows a graph 1500, where the frequency is in megahertz (MHz) along the X-axis, the surface pressure along the left Y-axis of the graph 1500 is in decibels (dB), and the surface pressure along the right Y-axis of the graph 1500 is in dB. Curve 1502 (e.g., shown as a solid curve) shows the Figure 4 transmission bandwidth of the CMUT 350 in edge mode activation (e.g., DC bias and AC signal are only applied to the vertical electrodes or edge electrodes) with respect to the surface pressure indicated on the right side of the graph 1500. Curve 1504 (e.g., shown as a dashed curve) shows the Figure 4 transmission bandwidth of the CMUT 350 in dual-mode activation (e.g., DC bias is applied to the vertical electrodes or edge electrodes and AC signal is applied to the horizontal electrodes or in-plane electrodes). As Figure 9 depicted in Figure 4 , due to the addition of AC actuated electromechanical coupling on the in-plane electrodes, during dual-mode activation, the

[0071] Figure 10 shows a series of exemplary graphs comparing the effects of in-plane electrode (e.g., horizontal electrode actuated by AC) coverage of an exemplary CMUT on pressure and bandwidth during dual-mode activation. Referring to Figure 10 , shows graphs 1510, 1512, 1514, and 1516, where the frequency is in MHz along the X-axis and the normalized pressure (normalized to 1) is along the Y-axis. Graphs 1510, 1512, 1514, and 1516 are for electrode coverage percentages of 25%, 33%, 50%, and 80% (e.g., relative to the mass radius) respectively. Curves 1518, 1520, 1522, and 1524 show the effects of in-plane electrode coverage on both pressure and bandwidth. For example, as the electrode coverage increases, the bandwidth decreases and the normalized pressure increases.

[0072] Similarly, Figure 11 shows an exemplary graph comparing the effects of in-plane electrode (e.g., horizontal electrode actuated by AC) coverage of an exemplary CMUT on pressure and bandwidth during dual-mode activation according to various embodiments. Referring to Figure 11Figure 1530 shows the curves, where the frequency along the X-axis is in MHz and the normalized pressure (normalized to the corresponding maximum) along the Y-axis. Curves 1532 (shown as a solid curve), 1534 (shown as a dashed curve), and 1536 (shown as a dashed curve) represent electrode coverage percentages of 25%, 33%, and 50%, respectively (e.g., relative to the mass radius). Curves 1532, 1534, and 1536 illustrate the effect of in-plane electrode coverage on both pressure and bandwidth. For example, as electrode coverage increases, bandwidth decreases. Figure 10 and Figure 11 As described, altering the in-plane electrode coverage area enables optimization of output power (e.g., acoustic power) and bandwidth.

[0073] Figure 12 and Figure 13 Schematic diagrams illustrating the manufacture of exemplary CMUTs with biplane out-of-plane and in-plane actuation and displacement according to various embodiments are shown. Figure 12 In the diagram, the fabrication of the plate and substrate having the vertical and horizontal electrodes discussed above is shown respectively in the corresponding... Figure 3 The left and right sides. The various manufacturing steps are similar, but the plate and substrate have complementary orientations. It should be noted that only portions of the plate and substrate are shown, and the parts are not drawn to scale. In addition to those described below, the plate and substrate may undergo other manufacturing steps.

[0074] like Figure 12 The depiction involves etching (e.g., deep reactive ion etching (DRIE)) a wafer (e.g., a silicon wafer) to form mass blocks in a plate and recesses in a substrate. Following etching, metal is deposited onto the plate and substrate on surfaces facing each other (e.g., a horizontal surface and a vertical surface) via metal deposition. The metal is then etched to form corresponding horizontal and vertical electrodes on the plate and substrate. After metal etching, an insulating layer or high contact resistance material may be disposed on the in-plane electrodes or horizontal electrodes of the plate and substrate and etched. In some embodiments, the corresponding insulating layer is disposed on both the plate and the substrate. In other embodiments, the insulating layer is disposed only on the plate. In other embodiments, the insulating layer is disposed only on the substrate. After fabricating the plate and substrate with electrodes and insulating layers, as... Figure 13 As shown, the board and substrate are bonded together to form the CMUT (and the closed gap between the board and the substrate) (e.g., corresponding to...). Figure 3 ).

[0075] The technical effects of the disclosed subject matter include providing a CUMT with both out-of-plane and in-plane actuation and displacement. Specifically, a direct current (DC) signal can be applied to a pair of vertical electrodes (e.g., for out-of-plane actuation) and an alternating current (AC) signal can be applied to a pair of horizontal electrodes (e.g., for in-plane actuation). Actuation with a DC signal is orthogonal to the displacement direction of the central mass block of the plate toward the recess of the substrate, while actuation with an AC signal is parallel to the displacement direction. In-plane actuation with an AC signal increases the electromechanical coupling factor compared to a CMUT device with only edge electrodes. This allows the CMUT to have a higher transmit bandwidth during dual-mode activation when a DC signal is applied to a pair of vertical electrodes and an AC signal is applied to a pair of horizontal or in-plane electrodes, which is completely different from when both AC and DC signals are applied to the pair of vertical electrodes during edge-mode activation. The disclosed CMUT can operate in both a normal operating mode and a mechanical collapse operating mode. Additionally, the CMUT can operate in either edge-mode activation or dual-mode activation.

[0076] This written description uses examples to disclose the subject matter, including best practices, and also enables those skilled in the art to practice the disclosed subject matter, including making and using any device or system and performing any included methods. The patent scope of this subject matter is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that differ only slightly from the literal language of the claims.

Claims

1. A capacitor transducer, comprising: A plate, the plate including a protruding central mass block; A base having a central recess configured to receive the central mass block; A first electrode is coupled to the non-horizontal edge surface of the central mass block; The second electrode is coupled to the non-horizontal edge surface of the central recess; A third electrode, which is coupled to the horizontal edge surface of the central mass block; and A fourth electrode, which is coupled to the horizontal edge surface of the central recess; The plate is coupled to the substrate at least along the outer peripheral region of the plate and the substrate.

2. The capacitive transducer of claim 1, wherein the first electrode and the second electrode are configured to be actuated via a DC signal applied to the first electrode and the second electrode, and the third electrode and the fourth electrode are configured to be actuated via an AC signal applied to the third electrode and the fourth electrode.

3. The capacitive transducer according to claim 2, wherein the actuation of the DC signal is orthogonal to the displacement direction of the bottom surface of the central mass block of the plate toward the top surface of the central recess of the substrate, and wherein the actuation of the AC signal is parallel to the displacement direction.

4. The capacitive transducer of claim 1, wherein the capacitive transducer is configured to have a higher transmit bandwidth when a DC signal is applied to the first electrode and the second electrode and when an AC signal is applied to the third electrode and the fourth electrode, which is completely different from when both the AC signal and the DC signal are applied to the first electrode and the second electrode.

5. The capacitive transducer of claim 1, wherein the capacitive transducer is configured to operate in a transmit mode, a receive mode, and a transmit and receive mode.

6. The capacitive transducer of claim 5, wherein during operation in the transmission mode, only the AC signal is applied to the third and fourth electrodes, and a current signal is not applied to the first and second electrodes.

7. The capacitive transducer of claim 5, wherein during operation in the transmit and receive modes, a DC signal is applied to the first and second electrodes during transmission, and an AC signal is applied to the third and fourth electrodes, and both the AC signal and the DC signal are applied to the third and fourth electrodes during reception.

8. The capacitive transducer of claim 7, wherein during operation in the transmit and receive modes, the voltage level of the DC signal is different during the transmit phase compared to the receive phase.

9. The capacitive transducer according to claim 1, comprising a first insulating layer disposed on a portion of the third electrode, a second insulating layer disposed on a portion of the fourth electrode, or both a first insulating layer disposed on a portion of the third electrode and a second insulating layer disposed on a portion of the fourth electrode.

10. The capacitive transducer according to claim 1, comprising a horizontal gap between the first electrode and the second electrode and a vertical gap between the third electrode and the fourth electrode.

11. The capacitive transducer according to claim 1, wherein the non-horizontal edge surface of the central mass block and the non-horizontal edge surface of the central recess are substantially vertical surfaces.

12. The capacitive transducer according to claim 1, wherein the non-horizontal edge surface of the central mass block and the non-horizontal edge surface of the central recess are angular surfaces.

13. The capacitive transducer according to claim 1, wherein the horizontal edge surface of the central mass block and the non-horizontal edge surface of the central recess are substantially horizontal surfaces.

14. The capacitive transducer according to claim 1, wherein the non-horizontal edge surface of the central mass block and the non-horizontal edge surface of the central recess are rounded surfaces.

15. The capacitive transducer according to claim 1, wherein the non-horizontal edge surface of the central mass block and the non-horizontal edge surface of the central recess are corrugated surfaces.

16. An ultrasonic system comprising a capacitive transducer according to any one of claims 1 to 15.

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