Low-voltage / low-power MEMS transducer with direct interconnection function

Abstract

To provide a low-voltage / low-power MEMS transducer with a direct interconnection function.SOLUTION: An imaging device (120) includes a two-dimensional array (2000) of piezoelectric elements. Each piezoelectric element (2002) includes a piezoelectric layer; a lower electrode (2003) disposed on the lower side of the piezoelectric layer and configured to receive a transmission signal during a transmission mode and to form a load during a reception mode; an upper electrode (2006) disposed on the upper side of the piezoelectric layer; and a first conductor (2007). The first upper electrode, the part of the piezoelectric element in a first row of the secondary array (2000), is electrically connected to the first conductor (2007).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 62,429,832, filed on December 4, 2016, entitled "A Configurable Ultrasonic Line imager", U.S. Provisional Application No. 62,429,833, filed on December 4, 2016, entitled "Low Voltage, Low Power MEMS Transducer with Direct Interconnect" and U.S. Provisional Application No. 62,433,782, filed on December 13, 2016, entitled "Micromachined Transceiver Array". The contents of these applications are hereby incorporated by reference in their entirety.

[0002] A. Technical Field The present invention relates to imaging devices, and more particularly, to imaging devices having a configurable ultrasonic line imager.

Background Art

[0003] B. Background of the Invention Non - invasive imaging systems for imaging internal tissues, bones, blood flow, or organs of a human or animal body and displaying the images require transmitting signals into the body and receiving reflected signals from the body part being imaged. Typically, the transducers used in imaging systems are called transceivers, and some of the transceivers are based on the photoacoustic effect or the ultrasonic effect. Generally, transceivers are used for imaging, but are not necessarily limited to imaging. For example, transceivers can be used in medical imaging, in - tube flow measurement, speaker and microphone arrays, lithotripsy, localized tissue heating for treatment, or high - intensity focused ultrasound (HIFU) for surgery. From bulk piezoelectric (PZT) materials Conventional transducers that are constructed typically require very high voltages to generate the transmit signal, typically pulses of 100V or more. This high voltage translates to high power dissipation, since the power consumption / dissipation in the transducer is proportional to the square of the driving voltage. There is also a limit to how hot the surface of the probe can get, and since the power consumption is proportional to the heat generated by the probe, this limits how much power can be dissipated in the probe. In conventional systems, the heat generation requires cooling devices for some probes, increasing the manufacturing cost and weight of the probe. In general, the weight of conventional probes is also an issue, since many ultrasound technicians using these probes are known to suffer from muscle injuries.

[0004] Conventional ultrasound probes used in medical imaging typically use PZT materials or other piezoelectric A ceramic and polymer composite is used. The probe typically houses the transducer and some other electronic circuitry with a means for displaying an image on a display unit. To fabricate a conventional bulk PZT element for a transducer, one simply cut a thick piezoelectric material These rectangular PZT elements are manufactured by cutting a slab of material into large rectangular PZT elements. The manufacturing process involves precisely cutting rectangular slabs of thick PZT or ceramic material and placing them on a substrate at precise intervals. The manufacturing costs are very high due to the mounting involved. Furthermore, the impedance of the transducer is much higher than the impedance of the transmitting and receiving electronics for the transducer.

[0005] In conventional systems, the transmit and receive electronics for the transducer are often located far away from the probe, requiring a small coaxial cable between the transducer and the electronics. Typically, the cable needs to have the correct length for delay and impedance matching, and for efficient connection of the transducer to the electronics through the cable. Quite often, an additional impedance matching network is required.

[0006] Advances in micromachining technology have enabled sensors and actuators, such as capacitive micromachined ultrasonic transducers (cMUTs) and piezoelectric micromachined ultrasonic transducers (pMUTs), to be efficiently formed on a substrate. Compared to conventional transducers with bulk piezoelectric materials, pMUTs have simpler and higher-performance interconnections between the electronic circuit and the transducer, offer greater flexibility at the operating frequency, and provide the possibility of generating higher-quality images, while being less bulky and less expensive.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The basic concepts of these transducers were disclosed in the early 1990s, but the commercial implementation of these concepts faces many challenges. For example, conventional cMUT sensors are susceptible to impairments or performance drifts due to charge accumulation during high-voltage operation, are difficult to generate sufficiently high acoustic pressure at low frequencies, and are inherently non-linear. Conventional pMUTs were a promising alternative but had problems regarding transmission and reception inefficiencies, still required a relatively high operating voltage, and had a limited bandwidth. Therefore, there is a need for pMUTs that have improved efficiency, can operate at lower voltages, and can exhibit a high bandwidth.

MEANS FOR SOLVING THE PROBLEMS

[0008] In an embodiment, the imaging device includes a two-dimensional array of piezoelectric elements. Each piezoelectric element includes: a piezoelectric layer; a lower electrode disposed below the piezoelectric layer and configured to receive a transmission signal during a transmission mode and to form a charge during a reception mode; a first upper electrode disposed above the piezoelectric layer; and a first conductor, and the first upper electrodes of some of the piezoelectric elements in a first column of the two-dimensional array are electrically coupled to the first conductor.

[0009] In an embodiment, the imaging device is a two-dimensional array of piezoelectric elements, each piezoelectric element of the two-dimensional array of piezoelectric elements includes at least one sub-piezoelectric element, a piezoelectric layer; a lower electrode disposed below the piezoelectric layer; and a two-dimensional array including first and second upper electrodes disposed above the piezoelectric layer; a first conductor, wherein a part of the first upper electrodes of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the first conductor; a first electrical circuit electrically coupled to the first conductor and configured to process a signal received through the first conductor; a second conductor, wherein a part of the second upper electrodes of the piezoelectric elements in the second column of the two-dimensional array are electrically coupled to the second conductor; a switch having a first end and a second end, the first end being electrically coupled to the second conductor; a second electrical circuit for processing a signal; and a transmission driver for sending a signal to the second conductor, the second end of the switch being selectively coupled to one of the second electrical circuit and the transmission driver.

[0010] In an embodiment, the imaging device is a two-dimensional array of piezoelectric elements, each piezoelectric element of the two-dimensional array of piezoelectric elements includes at least one sub-piezoelectric element, a piezoelectric layer; a lower electrode disposed below the piezoelectric layer; and a two-dimensional array having first and second upper electrodes disposed above the piezoelectric layer; a first conductor, wherein a part of the first upper electrodes of the piezoelectric elements in the first row of the two-dimensional array are electrically coupled to the first conductor; a first electrical circuit electrically coupled to the first conductor and configured to process a signal received through the first conductor; a second conductor, wherein a part of the second upper electrodes of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the second conductor; a switch having a first end and a second end, the first a switch, one end of which is electrically coupled to the second conductor; a second electrical circuit for processing signals; and a transmission driver for sending signals to the second conductor, wherein the second end of the switch is selectively coupled to one of the second electrical circuit and the transmission driver.

[0011] In an embodiment, the imaging device includes a transceiver substrate and an application specific integrated circuit (ASIC) chip. The transceiver substrate includes: a two-dimensional array of piezoelectric elements, each piezoelectric element of the two-dimensional array of piezoelectric elements having: a piezoelectric layer; a lower electrode disposed under the piezoelectric layer; first and second upper electrodes disposed above the piezoelectric layer; and first and second conductors electrically coupled to the first and second upper electrodes, respectively. The ASIC chip has: a two-dimensional array of circuit elements, each circuit element of the two-dimensional array of circuit elements having: a first electrical circuit electrically coupled to the first conductor of the piezoelectric element and configured to process signals received through the first conductor; a switch having a first end and a second end, the first end of which is electrically coupled to the second conductor of the piezoelectric element; a second electrical circuit for processing signals; and a transmission driver for sending signals to the second conductor, wherein the second end of the switch is selectively coupled to one of the second electrical circuit and the transmission driver.

[0012] In an embodiment, an electric circuit for controlling a plurality of piezoelectric elements includes: a first conductor for transmitting a drive signal to one or more of the plurality of piezoelectric elements during a transmission mode; and a second conductor for transmitting a sensor signal from one or more of the plurality of piezoelectric elements during a reception mode. Each circuit element of the plurality of circuit elements includes: a first switch having a first end electrically coupled to the second conductor and a first electrode of the piezoelectric element; a second switch having a first end and a second end, wherein the first end of the second switch is electrically coupled to the first conductor; a transmission driver configured to transmit a signal to the first electrode of the piezoelectric element when receiving a signal through the second end of the second switch, the second end of the second switch being electrically coupled to the transmission driver; and a third switch having a first end and a second end, wherein the first end of the third switch is electrically coupled to the second end of the second switch, and the second end of the third switch is electrically coupled to an electrode of the piezoelectric element.

[0013] In an embodiment, a method of polling a piezoelectric element electrically coupled to an application specific integrated circuit (ASIC) chip, the piezoelectric element including a lower electrode, a piezoelectric layer disposed on the lower electrode, and first and second upper electrodes disposed on the piezoelectric layer, the method includes: electrically connecting the lower electrode to ground; applying a positive voltage to the first upper electrode; applying a negative voltage to the second upper electrode; and exposing the piezoelectric element to a certain temperature over a long period of time, whereby a first portion of the piezoelectric layer under the first upper electrode is poled in a first direction and a second portion of the piezoelectric layer under the second upper electrode is poled in a second direction opposite to the first direction.

[0014] In an embodiment, the imaging device includes a two-dimensional array of piezoelectric elements, each piezoelectric element including at least one sub-piezoelectric element, a piezoelectric layer, a lower electrode disposed below the piezoelectric layer, and a first upper electrode disposed above the piezoelectric layer. The imaging device further includes an application-specific integrated circuit (ASIC) chip having an array of circuits for driving the two-dimensional array of piezoelectric elements, each of the circuits being electrically coupled to a corresponding piezoelectric element. A first line imager including a portion of the piezoelectric elements within a first column of the two-dimensional array is formed by simultaneously turning on a portion of the circuits that control the portion of the piezoelectric elements within the first column of the two-dimensional array.

Brief Description of the Drawings

[0015] Reference is made to embodiments of the present invention. Examples of embodiments may be shown in the accompanying drawings. These drawings are intended to be illustrative rather than limiting. While the invention will generally be described in the context of these embodiments, it should be understood that the scope of the invention is not intended to be limited to these particular embodiments.

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DETAILED DESCRIPTION OF THE INVENTION

[0065] In the following description, for purposes of explanation, specific details are set forth in order to provide an understanding of the disclosure. It will be apparent, however, to one skilled in the art that the disclosure may be practiced without these specific details. Further, one skilled in the art will recognize that the embodiments of the disclosure described below may be implemented in a variety of ways, such as a process, apparatus, system, device, or method on a tangible computer-readable medium.

[0066] One skilled in the art will recognize that: (1) certain manufacturing steps may be optionally performed; (2) the steps need not be limited to the specific order described herein; and (3) certain steps may be performed in different orders, including being performed simultaneously.

[0067] The elements / components shown in the figures illustrate exemplary embodiments of the present disclosure and are intended to avoid obscuring the present disclosure. In the specification, references to "one embodiment", "preferred embodiment", "an embodiment" or "embodiments" mean that the specific features, structures, characteristics or functions described in connection with that embodiment are included in at least one embodiment of the present disclosure and may be included in a plurality of embodiments. The appearance of the phrases "in one embodiment", "in an embodiment", or "in embodiments" throughout the specification does not necessarily refer to the same embodiment(s). The terms "comprising", "including", "having", and "containing" are to be understood as open terms, and the lists accompanying them are examples and are not intended to be limiting to the listed items. Any headings used in this specification are for organizational purposes only and are not used to limit the scope of the specification or claims. Further, the use of certain terms in various places in the specification is for illustrative purposes and should not be construed as limiting.

[0068] In embodiments, pMUT transducers and transducer assemblies can be used to generate images of internal organs of the human / animal body and for other therapeutic applications such as heating tissue for treatment or focusing high-power ultrasonic beams for microsurgery using ultrasonic beams. In embodiments, piezoelectric elements may be used for tomographic applications.

[0069] In an embodiment, the manufacturing cost of the pMUT can be reduced by applying modern semiconductor and wafer processing technologies. In an embodiment, the thin film piezoelectric layer may be spun or sputtered onto a semiconductor wafer and later patterned to form piezoelectric sensors each having two or more electrodes. In an embodiment, each piezoelectric element may be designed to emit or receive signals at a certain frequency known as the center frequency, as well as at second and / or additional frequencies. Hereinafter, the terms piezoelectric element, pMUT, transceiver, and pixel are used interchangeably.

[0070] FIG. 1 shows a schematic diagram of an imaging system 100 according to an embodiment of the present disclosure. As shown in the figure, in a transmission mode / process, the system 100 includes an imager 120 that generates and transmits a pressure wave 122 toward an internal organ 112 such as a heart; and a device 102 that transmits and receives signals to and from the imager through a communication channel 130. In an embodiment, the internal organ 112 may reflect a part of the pressure wave 122 toward the imager 120, and the imager 120 may capture the reflected pressure wave and generate an electrical signal in a reception mode / process. The imager 120 may communicate the electrical signal to the device 102, and the device 102 may use the electrical signal to display an image of the organ or target on a display / screen 104.

[0071] In an embodiment, the imager 120 can be used to perform one-dimensional imaging also known as A-scan, two-dimensional imaging also known as B-scan, three-dimensional imaging also known as C-scan, and Doppler imaging. Also, the imager can be switched between various imaging modes under program control.

[0072] In an embodiment, the imager 120 may be used to obtain images of the internal organs of an animal. The imager 120 may also be used to determine the direction and velocity of blood flow in arteries and veins, as in Doppler-mode imaging, and to measure the hardness of tissue. In an embodiment, the pressure wave 122 may be an acoustic wave, an ultrasonic wave, or a photoacoustic wave that can pass through a human / animal body and be reflected by internal organs, tissues, or arteries and veins.

[0073] In an embodiment, the imager 120 may be a portable device and may communicate signals with the device 102 through the communication channel 130 wirelessly (using a protocol such as the 802.11 protocol) or via a cable (such as USB2, USB 3, USB 3.1, and USB-C). In an embodiment, the device 102 may be a mobile device such as a mobile phone or an iPad (registered trademark), or a stationary computing device that can display images to the user.

[0074] In an embodiment, the imager may be configured to simultaneously transmit and receive ultrasonic waveforms. Certain piezoelectric elements may be configured to send pressure waves toward the target organ being imaged, while other piezoelectric elements may receive the pressure waves reflected from the target organ and generate an electric charge in response to the received waves.

[0075] FIG. 2 shows a schematic diagram of the imager 120 according to an embodiment of the present disclosure. In the embodiment, the imager 120 may be an ultrasonic imager. As depicted in FIG. 2, the imager 120 includes: one or more transceiver tiles 210 for transmitting and receiving pressure waves; a coating layer 212 that operates as a lens for controlling the propagation direction of the pressure wave and / or focusing the pressure wave and also functions as an impedance interface between the transceiver tile and the human body 110; a control unit 202, such as an ASIC chip (or simply ASIC) coupled to the transducer tile 210 by bumps, for controlling the transceiver tile 210; a field programmable gate array (FPGA) 214 for controlling the components of the imager 120; one or more circuits 215, such as an analogue front end (AFE), for processing / conditioning the signals; an acoustic absorption layer 203 for absorbing the waves generated by the transducer tile and propagating towards the circuit 215; a communication unit 208 for communicating data with an external device, such as the device 102, through one or more ports 216; a memory 218 for storing data; a battery 206 for providing power to the components of the imager; and optionally, a display 217 for displaying an image of the target organ.

[0076] In an embodiment, the device 102 may have a display / screen. In such a case, the imager 120 may not include a display. In an embodiment, the imager 120 may receive power from the device 102 through one of the ports 230. In such a case, the imager 120 may not include the battery 206. Note that one or more of the components of the imager 120 may be combined into one integrated electrical element. Similarly, each component of the imager 120 may be implemented in one or more electrical elements.

[0077] In an embodiment, before the body 110 comes into direct contact with the coating layer 212, the user may apply a gel on the skin of the human body 110. Thereby, impedance matching at the interface between the coating layer 212 and the human body 110 can be improved, that is, at the interface, the loss of the pressure wave 122 at the interface is reduced, and the loss of the reflected wave toward the imager 120 is also reduced. In an embodiment, the transceiver tile 210 may be mounted on a substrate or attached to an acoustic absorber layer. This layer absorbs any ultrasonic signal radiated in the opposite direction. Without this absorption, the ultrasonic signal radiated in the opposite direction may be reflected and may interfere with the image quality.

[0078] As discussed below, the coating layer 212 may simply be a flat matching layer only for maximizing the transmission of acoustic signals from the transducer to the body and vice versa. In an embodiment, the thickness of the coating layer 212 may be one quarter wavelength of the pressure wave generated by the transducer tile 202. Since the beam focus in the elevation direction along the length direction of the column can be electronically implemented in the control unit 202, it is not essential in this case. Still, in some cases, a focused lens may be designed. The imager 120 generates an image of the organ 112 using the reflected signal, and the results may be displayed on the screen in various formats such as graphs, plots, and statistics with or without the image of the organ 112. may be displayed on the screen in various formats such as graphs, plots, and statistics.

[0079] In an embodiment, a control unit 202 such as an ASIC may be assembled as one unit together with the transceiver tile. In other embodiments, the control unit 202 may be located outside the imager 120 and may be electrically coupled to the transceiver tile 210 via a cable. In an embodiment, the imager 120 may include a housing surrounding the components 202-215 and a heat dissipation mechanism for dissipating the thermal energy generated by those components.

[0080] Figure 3A shows a schematic diagram of an exemplary transceiver array having three transceiver tiles 210 according to an embodiment of the present disclosure. The tiles may be on a plane or a curved surface. Figure 3B shows a top view of a transceiver tile 210 including one or more piezoelectric elements 302 according to an embodiment of the present disclosure. As shown, the transceiver tile 210 may include a transceiver substrate 304 and one or more piezoelectric elements 302 disposed on the transceiver substrate 304.

[0081] Unlike conventional systems using bulk piezoelectric elements, in an embodiment, the pMUT array 302 may be formed on a wafer, and the wafer may be diced to form a plurality of transceiver tiles 210. This process can manufacture a large number of transceiver tiles 210 at low cost, thus reducing the manufacturing cost. In an embodiment, the diameter of the wafer may be in the range of 6 to 12 inches, and many pMUT arrays can be batch manufactured In the embodiments discussed in connection with FIGS. 18 and 19, the integrated circuit for controlling the pMUT array 302 may be formed within an ASIC chip. As a result, the pMUT array 302 may preferably be connected to a matching integrated circuit in proximity within 25 μm to 100 μm. For example, the transceiver tile 210 may have 1024 pMUT elements 302 and may be connected to a matching ASIC chip having an appropriate number of circuits for driving the 1024 pMUT elements 302.

[0082] In an embodiment, each piezoelectric element 302 may have any suitable shape such as a square, rectangle, and circle. In an embodiment, two or more piezoelectric elements may be connected to form a larger pixel element. As shown in FIG. 3B, when constructing an imager, it is desirable to have a two-dimensional array of piezoelectric elements 302 arranged in orthogonal directions. In an embodiment, to create a line element, a column of N piezoelectric elements 302 is electrically parallel It may be connected to. Then, this line element can provide transmission and reception of ultrasonic signals similar to those achieved by each element, with a continuous pressure approximately N times the length of each element. It can provide transmission and reception of ultrasonic signals similar to those achieved by piezoelectric elements. This line element may alternatively be called a column or a line or a line element. It is understood that the tiles may be arranged in other shapes such as circular or other shapes. In an embodiment, one or more temperature sensors 320 may be installed within the transducer tile 210 to measure the temperature of the tile 210. Note that the imager 120 may include one or more temperature sensors for measuring the temperature at various positions of the imager 120. To mimic a line element of a conventional design, the shape of a piezoelectric element of a given width needs to be very tall. For example, a line element of a conventional design may have a width of 280 μm and a height of 8000 μm, and a thickness of 100 μm. However, on the transceiver tile

[0083] 210, it is advantageous to design a line element using a plurality of identical piezoelectric elements 302, and each element may have its characteristic center frequency. In an embodiment, when a plurality of piezoelectric elements 302 are connected together, the composite structure (i.e., the line element) can act as one line element with a center frequency consisting of the center frequencies of all element pixels. In modern semiconductor processes, these center frequencies match well with each other and have a very small deviation from the center frequency of the line element. It is also possible to mix some pixels with somewhat different center frequencies to create a line with a wider bandwidth compared to a line using only one center frequency. In an embodiment, when the piezoelectric element 302 is exposed to stimulation at its center frequency, it vibrates at that center frequency and is accompanied by a suspended membrane that behaves like a resonator. These resonators have selectivity known as the Q factor. In an embodiment, for an ultrasonic imager It may be connected to. Then, this line element can provide transmission and reception of ultrasonic signals similar to those achieved by each element, with a continuous pressure approximately N times the length of each element.

[0084] In an embodiment, when the piezoelectric element 302 is exposed to stimulation at its center frequency, it vibrates at that center frequency and is accompanied by a suspended membrane that behaves like a resonator. These resonators have selectivity known as the Q factor. In an embodiment, for an ultrasonic imager Thus, Q may typically be designed to be low (close to or around 1), and may be achieved in actual use by a combination of pixel design and the load applied to the pixels. In an embodiment, the load may be provided by applying a layer of RTV or other material to the upper surface of the piezoelectric element, and the load may facilitate closer impedance matching between the transducer surface that emits and receives pressure waves and the body part being imaged. In an embodiment, low Q and well-matched center frequencies may allow the line elements to act essentially like a line imaging element having substantially one center frequency. In an embodiment, the load may also include a matching layer under the transducer, where the emitted waveform is absorbed by an acoustic absorber. In an embodiment, for example, each piezoelectric element 302 may be spaced 250 μm apart from each other at the centers. For further simplification, assume they are square in shape. Here, for the sake of mimicking a conventional line element, the piezoelectric elements 302 in a column may be connected to each other. For example, 24 piezoelectric elements 302 in a column may form a line element with a height of about 6 mm, and each element has a width of 0.25 mm. In an embodiment, this connection may be achieved at the wafer level using a metal interconnect layer. In an embodiment, for example, each piezoelectric element 302 may be spaced 250 μm apart from each other at the centers. For further simplification, assume they are square in shape. Here, for the sake of mimicking a conventional line element, the piezoelectric elements 302 in a column may be connected to each other. For example, 24 piezoelectric elements 302 in a column may form a line element with a height of about 6 mm, and each element has a width of 0.25 mm. In an embodiment, this connection may be achieved at the wafer level using a metal interconnect layer.

[0085] In an embodiment, for example, each piezoelectric element 302 may be spaced 250 μm apart from each other at the centers. For further simplification, assume they are square in shape. Here, for the sake of mimicking a conventional line element, the piezoelectric elements 302 in a column may be connected to each other. For example, 24 piezoelectric elements 302 in a column may form a line element with a height of about 6 mm, and each element has a width of 0.25 mm. In an embodiment, this connection may be achieved at the wafer level using a metal interconnect layer. In an embodiment, for example, each piezoelectric element 302 may be spaced 250 μm apart from each other at the centers. For further simplification, assume they are square in shape. Here, for the sake of mimicking a conventional line element, the piezoelectric elements 302 in a column may be connected to each other. For example, 24 piezoelectric elements 302 in a column may form a line element with a height of about 6 mm, and each element has a width of 0.25 mm. In an embodiment, this connection may be achieved at the wafer level using a metal interconnect layer.

[0086] Note that the transceiver tile 210 may include one or more membranes suspended from a substrate, and the piezoelectric element 302 may be disposed on the membrane. In an embodiment, as described below in connection with FIGS. 4-8, the membrane may be disposed under each of the piezoelectric elements 302. In an embodiment, a plurality of piezoelectric elements may be disposed on one membrane 309. In an embodiment, two or more membranes may be disposed under one of the piezoelectric elements 302. Further information regarding the placement of piezoelectric elements on the membrane can be found in co-pending U.S. Patent Application No. 15 / 820,319, filed Nov. 21, 2017, entitled "Imaging Device with Piezoelectric Transducer", which is hereby incorporated by reference in its entirety.

[0087] In a conventional bulk piezoelectric element, the voltage potential between the upper electrode and the lower electrode is in the range of 100 V to 200 V. In a conventional pMUT, the voltage potential between the upper electrode and the lower electrode is about 30 V. In an embodiment, to further reduce this voltage, the piezoelectric element 302 may include a scaled-down thin piezoelectric layer, which may have a thickness on the order of 2 μm or less. FIGS. 4-8 illustrate steps for manufacturing an exemplary piezoelectric element according to an embodiment of the present disclosure. FIG. 4 shows a top view of a membrane 406 disposed on a substrate 402, and FIG. 5 shows a cross-sectional view of the membrane and the substrate taken along line 4-4 according to an embodiment of the present disclosure. (Embodiment In this state, the substrate 402 may correspond to the transceiver substrate 304 of FIG. 3B. As shown, in an embodiment, a film layer 404 may be deposited on the substrate 402, and a cavity 408 may be formed to remove a part of the substrate 402, thereby forming a membrane 406 that can vibrate in a direction perpendicular to the substrate 402. In an embodiment, the cavity 408 may be formed by ordinary wafer processing techniques such as etching. In an embodiment, the substrate 402 may be formed of the same material as the film layer 404. In an alternative embodiment, the substrate 402 may be formed of a material different from the film layer 404. Note that the cavity 408 may be formed after other components such as the upper conductor (812 in FIG. 8) of the piezoelectric element are formed.

[0088] In an embodiment, the membrane 406 has a circular projected area. However, it should be apparent to those skilled in the art that the membrane 406 may have other suitable geometric shapes.

[0089] FIG. 6 shows a top view of the lower electrode 602 disposed on the film layer 404 and above the membrane 406 according to an embodiment of the present disclosure. FIG. 7 shows a top view of the piezoelectric layer 706 disposed on the lower electrode 602 according to an embodiment of the present disclosure. In an embodiment, the piezoelectric layer 706 may have a projected area similar to that of the lower electrode 602, and as a result, the piezoelectric layer 706 may cover the entire portion of the lower electrode 602.

[0090] FIG. 8 shows a top view of a piezoelectric element according to an embodiment of the present disclosure. As shown, an upper electrode 808 may be disposed on the piezoelectric layer 706 and may be disposed above the film 406. In an embodiment, a conductor 812 may be disposed on the upper electrode 808 and electrically coupled to the upper electrode 808, while the conductors 810 and 811 may reach the lower electrode 602 through one or more vias 814. In an embodiment, the upper electrode 808, the piezoelectric layer 706, and the lower electrode 602 may form a two-terminal piezoelectric element, and the film 406 may vibrate when a voltage is applied between the upper electrode and the lower electrode. In an embodiment, charges may be formed at the upper and lower electrodes when the film is deformed by a pressure wave during the reception mode / process.

[0091] FIG. 9 shows a schematic diagram of a piezoelectric element 900 according to an embodiment of the present disclosure. As shown, the piezoelectric layer 910 may be disposed between a first electrode (X) 906 and a second electrode (O) 904. In an embodiment, the first electrode (X) 906 may be connected to ground or a DC bias via a conductor (X) 908, and the second electrode (O) 904 may be connected to an electrical circuit (not shown in FIG. 9) through a signal conductor (O) 902. In an embodiment, the piezoelectric element 800 of FIG. 8 is an exemplary implementation of the piezoelectric element 900, and the piezoelectric element 900 may be disposed on a film layer (such as 404 of FIG. 5).

[0092] In a conventional piezoelectric element, the piezoelectric layer is thick, approaching about 100 μm, and in order to generate an ultrasonic pressure wave strong enough to enable medical imaging, typically an AC voltage of +100 to -100 V is required across the piezoelectric layer. The frequency of this AC drive signal is typically near the resonance frequency of the piezoelectric structure and typically exceeds 1 MHz in medical imaging applications. In a conventional system, the power dissipated when driving a piezoelectric element is proportional to C*V 2 where C is the capacitance of the piezoelectric element and V is the maximum voltage across the piezoelectric layer. Typically, to transmit a pressure wave and When this occurs, multiple piezoelectric lines are driven together with somewhat different phase delays to focus a pressure wave or steer the propagation direction of the pressure wave. Simultaneous driving of the multiple piezoelectric lines raises the temperature of the surface of the piezoelectric element. Generally, it is highly desirable not to exceed a certain threshold temperature so as not to damage the object being imaged. This limits the number of lines that can be driven and the duration of the driving period.

[0093] In an embodiment, the piezoelectric layer 910 is much thinner compared to a conventional bulk piezoelectric element, having a thickness of about 1 - 2 μm. In an embodiment, this substantial reduction in thickness enables using a lower voltage drive signal for the piezoelectric element 900. Here, to maintain the same electric field strength, the voltage is lowered by approximately the amount by which the thickness of the piezoelectric layer 910 is reduced. For example, in an embodiment, the voltage potential applied to the two electrodes 904 and 906 can range from about 1.8 V to 12.6 V peak - to - peak. The capacitance of the piezoelectric element 900 can increase due to the reduction in the thickness of the piezoelectric layer 910 for a similar piezoelectric material. For example, if the drive voltage is reduced by a factor of 10 and the thickness of the piezoelectric layer 910 is also reduced by a factor of 10, the capacitance increases by a factor of 10 and the power dissipation decreases by a factor of 10. This reduction in power dissipation also reduces heat generation and temperature rise in the piezoelectric element. Thus, in an embodiment, a lower drive voltage and a thinner piezoelectric layer can be used compared to a conventional piezoelectric element to lower the temperature of the pMUT surface. Alternatively, in an embodiment, for a given temperature, more pMUT elements can be driven simultaneously compared to a conventional piezoelectric element to irradiate a larger target area. This can allow for a faster scan of the target, especially when multiple emissions are required to scan the entire portion of the target to form an image. In an embodiment, the target area can be scanned with multiple emissions using different steering angles, and the resulting image data can be combined to obtain a higher - quality image.

[0094] Compared with conventional bulk piezoelectric elements, in embodiments, the ability to drive more piezoelectric elements simultaneously allows for more coverage of the transducer aperture per emission, minimizes the number of emissions required to cover the entire aperture, and thus can increase the frame rate. The frame rate measures how many times the target is imaged per minute. In particular, when tissue movement is involved it is desirable to image at a high frame rate because the moving tissue can blur the image. In embodiments, an imager 120 operating at a higher frame rate can generate higher quality images compared to conventional bulk piezoelectric elements.

[0095] In embodiments, the image quality can be improved by combining several frames of the image into one resulting, lower noise frame. In embodiments, this averaging technique can be implemented to enhance the image quality for a given increase in pMUT temperature by using low voltage and low power pMUTs at a higher frame rate compared to conventional bulk piezoelectric elements. In embodiments, an aperture synthesis method of ultrasonic imaging may be used to allow for image compounding. The different frames of the image may also use different steering angles or be from orthogonal steering directions to better view the target.

[0096] FIG. 10A shows a schematic view of a piezoelectric element 1000 according to an embodiment of the present disclosure. FIG. 10B shows a symbolic representation of the piezoelectric element 1000 in FIG. 10A. As shown, the piezoelectric element 1000 is similar to the piezoelectric element 900, except that the piezoelectric element 1000 has more than two electrodes. More specifically, the piezoelectric element 1000 has an upper electrode (O) 1 00. It may include a first lower electrode (X) 1006, a second lower electrode (T) 1012, a piezoelectric layer 1010 disposed between the upper electrode and the lower electrode, and three conductors 1002, 1008, and 1014 electrically coupled to the lower electrode and the upper electrodes 1004, 1006, and 1012, respectively. (Hereinafter, the terms "upper" and "lower" simply refer to the two opposite sides of the piezoelectric layer, and it is not necessarily the case that the upper electrode is disposed above the lower electrode.)

[0097] Although a unimorph piezoelectric element is shown in FIG. 10A for purely illustrative purposes, in embodiments, a multilayer piezoelectric element composed of a plurality of piezoelectric sub-layers and electrodes can be utilized. In an embodiment, the piezoelectric layer 1010 may include at least one of PZT, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF, and LiNiO3.

[0098] FIG. 10C shows a schematic cross-sectional view of a piezoelectric element 1000 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1000 may be disposed on a film layer 1034 supported by a substrate 1030. In an embodiment, a cavity 1032 may be formed in the substrate 1030 to define the film. In an embodiment, the film layer 1034 may be formed by depositing SiO2 on the substrate 1030.

[0099] In an embodiment, the piezoelectric element 1000 may include a piezoelectric layer 1010 and a first electrode (O) 1002 electrically connected to a signal conductor (O) 1004 . In an embodiment, the signal conductor (O) 1004 may be formed by depositing TiO2 and a metal layer on the film layer 1034 . In an embodiment, the piezoelectric layer 1010 may be formed by sputtering technology or by a sol-gel process.

[0100] In an embodiment, a second electrode (X) 1006 is grown on the piezoelectric layer 1010, It may be electrically connected to the second conductor 1008. The third electrode (T) 1012 may also be grown on the piezoelectric layer 1010 and disposed adjacent to the second conductor 1012, but may be electrically insulated from the second conductor (X) 1008. In an embodiment, the second electrode (X) 1006 and the third electrode (T) 1012 may be formed by depositing a single metal layer on the piezoelectric layer 1010 and patterning the metal layer. In an embodiment, the projected areas of the electrodes 1002, 1006, and 1012 may have any suitable shape such as a square, rectangle, circle, ellipse, etc.

[0101] Similar to the piezoelectric element 1000, the first electrode (O) 1002 may be electrically connected to the conductor (O) 1004 using a metal, via, and interlayer dielectric body. In an embodiment, the first electrode (O) 1002 may be in direct contact with the piezoelectric layer 1010. The third conductor (T) 1014 may be deposited or grown on the opposite side of the piezoelectric layer 1010 with respect to the first electrode (O) 1002 as well.

[0102] FIG. 10D shows a schematic diagram of a piezoelectric element 1030 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1030 may include two sub-piezoelectric elements (or simply sub-elements) 1031-1 and 1031-2. In an embodiment, each sub-element may be a three-terminal device, i.e., having one upper electrode 1032-1 (or 1032-2), two lower electrodes 1034-1 (or 1034-2), and 1036-1 (or 1036-2) and one piezoelectric layer 1035-1 (or 1035-2). In an embodiment, the upper electrode 1032-1 may be electrically connected to the upper electrode 1032-2 by a common conductor (O) 1031, and the first lower electrode (X) 1034-1 may be The first bottom electrode (X) 1034-2 may be electrically connected to the first bottom electrode (X) 1034-2 by a common conductor (X) 1038, and the second bottom electrode (T) 1036-1 may be electrically connected to the second bottom electrode (T) 1036-2 by a common conductor (T) 1040. The conductor (O) 1032-1 may be arranged on one film, or each sub-element may be arranged on a separate film. It should be apparent to one skilled in the art that the MOS 1032 may be electrically connected to the electrode (O) 1031 using metal, vias, interlayer dielectrics (ILD), and the like.

[0103] In an embodiment, conductor (X) 1038 and conductor (T) 1040 may all be grounded (or connected to a DC bias) during active operation of the imager. In an embodiment, electrodes (O) 1032-1 and 1032-2 share a common transmit driver circuit and a common The piezoelectric element 1030 may be driven by a common electrical signal, typically a signal waveform around the center frequency of the transducer. For example, if the center frequency is 2 MHz, then a 2 MHz sinusoidal or square waveform may be applied to the piezoelectric element 1030. This waveform may cause the piezoelectric element 1030 to resonate at 2 MHz and emit pressure waves, such as 122, from the surface of the transducer. The pressure waves may be reflected from the target organ being imaged. In an embodiment, the reflected pressure waves may strike the piezoelectric element 1030, which is now connected to a signal receiver. The pressure waves may be converted to charge in the piezoelectric element 1030 by the piezoelectric layers 1035-1 and 1035-2. In an embodiment, this charge is processed by amplifiers, filters, and finally A / D conversion. The signal is then digitized by a digital decimator (not shown in Figure 10D), followed by a digital decimator, and the data is finally interfaced to an FPGA or a graphical processing unit (GPU). These processed signals from the plurality of piezoelectric elements may then be reconstructed into an image. The signal waveform driving the transmission driver may be a frequency-varying signal, a phase-varying signal, or other complex encoded signals such as chirps or Golay codes. 。

[0104] FIG. 10E shows a schematic diagram of a piezoelectric element 1050 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1050 may include two sub-elements 1051-1 and 1051-2. In an embodiment, each sub-element may be a two-terminal device, that is, it may have one upper electrode 1052-1 (or 1052-2), one lower electrode 1054-1 (or 1054-2), and one piezoelectric layer 1056-1 (or 1056-2). In an embodiment, the upper electrode (O) 1052-1 may be electrically connected to the upper electrode (O) 1052-2 by a common conductor (O) 1051, and the lower electrode (X) 1054-1 may be electrically connected to the lower electrode (X) 1054-2 by a common conductor (X) 1058. In an embodiment, the piezoelectric element 1050 may be disposed on one film, or each sub-element may be disposed on a separate film.

[0105] FIG. 10F shows a schematic diagram of a piezoelectric element 1070 according to an embodiment of the present disclosure. FIG. 10G shows a bottom view of the piezoelectric element 1070 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1070 includes an upper electrode (O) 1074, a first lower electrode (X) 1080, a second lower electrode (T) 1076, a piezoelectric layer 1075 disposed between the upper electrode and the lower electrodes, and and may include three conductors 1072, 1078, and 1082 electrically coupled to the lower electrodes and the upper electrodes 1074, 1076, and 1080, respectively. (In FIG. 10G, the conductors are not shown.) In an embodiment, each of the first and second lower electrodes has an annular shape, and the second lower electrode (X) 1076 surrounds the first lower electrode (T) 1080.

[0106] FIG. 10H shows a schematic diagram of a piezoelectric element 1085 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1085 may utilize a transverse mode of operation and may include a substrate 1091, a film 1090 fixed to the substrate at one end, a lower electrode (O) 1092 electrically coupled to a conductor 1089, a piezoelectric layer 1088, and an upper electrode 1086 electrically coupled to a conductor 1087. In an embodiment, the film 1090 may be fixed to the substrate 1091 at one end so as to vibrate in a transverse mode as indicated by arrow 1093, i.e., the piezoelectric element may operate in a transverse mode. Note that the piezoelectric element 1085 may have any suitable number of upper electrodes. Also note that two or more piezoelectric elements may be disposed on the film 1090. Further note that the substrate 1091 and the film 1090 may be formed from a single monolithic body, or the film may be formed by etching the substrate.

[0107] Note that the piezoelectric element 1085 may have any suitable number of upper electrodes. Also note that two or more piezoelectric elements may be disposed on the film 1090. Further note that the substrate 1091 and the film 1090 may be formed from a single monolithic body, or the film may be formed by etching the substrate.

[0108] FIG. 11 shows a schematic diagram of a piezoelectric element 1100 according to an embodiment of the present disclosure. As shown, an electrode (O) 1104 may be disposed on the upper surface of a piezoelectric layer 1110 and may be electrically coupled to a conductor (O) 1102 that may be connected to an electrical circuit. A conductor (T1) 1108, a conductor (T2) 1114, and a conductor (X) 1118 may be connected to a lower electrode (T1) 1106, an electrode (T2) 1112, and an electrode (X) 1116, respectively. The electrode (T1) 1106, the electrode (X) 1116, and the electrode (T2) 1112 may be disposed on the lower surface of the piezoelectric layer 1110. In an embodiment, the piezoelectric element 1100 may be disposed on one film or three separate films. FIGS. 10A-11 each show a two-terminal (O and X) or three-terminal (O, X, and T) piezoelectric element

[0109] FIGS. 10A-11 each show a two-terminal (O and X) or three-terminal (O, X, and T) piezoelectric element or a piezoelectric element (or sub-element) having any one of four terminals (O, X, T1, and T2). However, it should be apparent to those skilled in the art that the piezoelectric element (or sub-element) may have more than four terminals. For example, the piezoelectric element may have an upper (O) electrode and more than three lower electrodes.

[0110] Figures 12 to 16 show steps for manufacturing an exemplary piezoelectric element having four terminals according to an embodiment of the present disclosure. Figure 12 shows a top view of a film 1206 that can be formed by forming a film layer 1204 on a substrate 1202 and forming a cavity 1208 in the substrate. Figure 13 shows a cross-sectional view of the structure of Figure 12 taken along line 12-12. In an embodiment, the film 1204 may be deposited by suitable wafer processing techniques.

[0111] Figure 14 shows a top view of a layer structure formed on the film layer 1204, and Figure 15 shows a cross-sectional view of the layer structure of Figure 14 taken along line 14-14 according to an embodiment of the present disclosure. As shown, three upper electrodes 1223, 1224-1, and 1224-2, a piezoelectric layer 1220, and a lower electrode 1222 may be formed on the film layer 1204. In an embodiment, the upper electrodes 1223, 1224-1, and 1224-2, the piezoelectric layer 1220, and the lower electrode 1222 may be deposited by suitable wafer processing techniques such as evaporation, sputtering, and patterning.

[0112] Figure 16 shows a top view of a piezoelectric element 1600 according to an embodiment of the present disclosure. As shown, three conductors 1620, 1622-1, and 1622-2 may be electrically coupled to the electrodes 1223, 1224-1, and 1224-2, respectively. Also, a conductor (O) 16 10 may be electrically coupled to the lower electrode 1222 through one or more vias 1614. In an embodiment, the electrical ground and the source plane are the vias 1614 and the conductor (O )It can reach the lower electrode 1222 through 1610. In an embodiment, each of the conductors 1620, 1622-1, and 1622-2 may be connected to ground or a DC bias voltage. In an embodiment, the conductor 1620 may be connected to ground or a first DC bias voltage, and the conductors 1622-1 and 1622-2 may be connected to ground or a second DC bias voltage.

[0113] Generally, due to the inherent asymmetry in the crystal structure of a piezoelectric material, an electric polarity develops, generating electric dipoles. In a macroscopic crystal structure, the dipoles are found to be randomly oriented by default, as shown to the left in FIG. 17A. When the material is subjected to mechanical stress, each dipole rotates from its original orientation in a direction that minimizes the total electrical and mechanical energy stored in the dipole. If all dipoles are initially randomly oriented (i.e., the net polarization is zero), their rotation may not significantly change the macroscopic net polarization of the material, and thus the piezoelectric effect shown would be negligible. Thus, during the initial state, the dipoles need to be oriented in somewhat the same direction, which is called the poling process. The direction in which the dipoles align is known as the poling direction. FIG. 17 shows the dipole orientation of a piezoelectric material before, during, and after the poling process according to an embodiment of the present disclosure.

[0114] As shown, before the poling process, the individual dipole moments are not aligned. During the poling process, the dipole moments can be aligned to face the same direction. After poling, the dipole moments can remain fairly aligned, but there may be some elements in random directions. In an embodiment, the poling process is performed by placing the piezoelectric material at a high temperature in a constant electric field, thereby forcing the dipoles to align.

[0115] In an embodiment, the piezoelectric element 1000 of FIG. 10A may be poled such that portions of the piezoelectric layer on the electrode (X) 1006 and the electrode (T) 1012 can be polarized in opposite directions. This type of poling can result in a boosted pressure output for the same transmission voltage compared to the pressure output obtained using one poling direction configuration. Also, in an embodiment, this type of poling can improve the reception sensitivity, where the reflected pressure wave can be differentially boosted to generate a larger charge output compared to one poling direction configuration.

[0116] FIG. 17B shows a flowchart of an exemplary process for poling a piezoelectric element 1600 according to an embodiment of the present disclosure. To pole the piezoelectric element 1600, the piezoelectric element 1600 may be mounted in a high-temperature chamber (step 1728), the lower electrode 1222 may be coupled to ground (step 1722), while the first upper electrode 1224-1 (or 1224-2) may be coupled to a high positive voltage such as 15 V (step 1724), and the second upper electrode 1223 may be coupled to a high negative voltage such as -15 V (step 1726). Then, the piezoelectric element 1600 may be exposed to a high temperature in the chamber for an extended period of time (step 1728).

[0117] Depending on the polarities of the first and second high voltages, the portions of the piezoelectric layer 1220 under the two electrodes 1224-1 and 1224-2 can be polarized in the same or opposite directions as the portion of the piezoelectric layer 1220 under the electrode 1223. In an embodiment, for example, poling can be performed for certain piezoelectric materials by applying a high voltage between the electrodes at a high temperature, typically 150°C, for 30 minutes. For example, for a piezoelectric layer with a thickness of 1 μm, +15 V from the signal electrode to the T electrode and -15 V from the signal electrode to the X electrode may be applied. Once the piezoelectric material is poled with, When energized, each of the X and T electrodes may be grounded or connected to a non - zero DC bias voltage, while the conductor (O) 1610 may be connected to the ASIC chip to be driven by a transmitter during the transmission operation, or may be connected to an LNA (e.g., 1811 in FIG. 18A) within the ASIC chip during the reception operation. In an embodiment, the DC bias voltage can improve the sensitivity of the piezoelectric element 1600. It may be connected to the ASIC chip so as to be driven by a driver, or may be connected to an LNA (e.g., 1811 in FIG. 18A) within the ASIC chip during the reception operation. In an embodiment, the DC bias voltage can improve the sensitivity of the piezoelectric element 1600.

[0118] FIG. 18A shows an imaging assembly 1800 according to an embodiment of the present disclosure. As shown, the imaging assembly 1800 may include a transceiver substrate 1802 (which may be similar to the transceiver tile 210) and an ASIC chip 1804 electrically coupled to the transceiver substrate. In an embodiment, the transceiver substrate 1802 may include one or more piezoelectric elements 1806, where each piezoelectric element may be disposed on one or more membranes. In an embodiment, two or more piezoelectric elements may be disposed on one membrane. In an embodiment, the poling of the piezoelectric layer may be performed after the transceiver substrate 1802 is interconnected to the ASIC chip 1804. Note that the ASIC 1804 may be replaced with a suitable substrate including a plurality of circuits for driving the piezoelectric elements 1806 within the transceiver substrate 1802.

[0119] In an embodiment, polling may be performed on the transceiver tile / substrate 1802 after the transceiver substrate is 3D interconnected to the ASIC chip 1804. In a conventional piezoelectric element, it is difficult to perform a polling process on the transceiver tile after the transducer tile is coupled to a circuit for driving the piezoelectric element, because polling requires applying a high voltage to the circuit for controlling the piezoelectric element, and such a high voltage may damage the circuit. In contrast, in an embodiment, polling may be performed on the transducer substrate 1802 that is already integrated with the ASIC chip 1804. In an embodiment, the ASIC chip 1804 enables applying a desired voltage to all first electrodes of the piezoelectric elements, and the high voltage may be applied to all second or additional electrodes.

[0120] In an embodiment, each of the piezoelectric elements 1806a-1806n may have two or more electrodes, and these electrodes may be connected to drive / receive electronic circuits housed within the ASIC chip 1804. In an embodiment, each piezoelectric element (e.g., 1806a) may include an upper conductor electrically connected to a conductor (O) (e.g., 1814a), and two lower electrodes electrically connected to conductors (X,T) (e.g., 1 810a and 1812a). In an embodiment, the conductor 1810a may be electrically coupled to a DC bias (X) 1832a or ground, and the conductor (T) 1812a may be coupled to a DC bias (T) 1834a or ground. In an embodiment, the ASIC chip 1804 may include one or more circuits 1842a-1842n electrically coupled to one or more of the piezoelectric elements 1806a-1806n, respectively, and one control unit 1840 for controlling the circuits 1842a-1842n. In an embodiment, each circuit (e.g., 1842a) includes a transmission driver (1813a), a receiver amplifier (or simply an amplifier) (e.g., 1811a), and a conductor (O) (1

[0121] 814a).A switch (e.g., 1816a) having one terminal electrically coupled to 814a) and another terminal that toggles between the two conductors coupled to transmission driver 1813a and amplifier 1811a may be included. During the transmit (Tx) mode / process, switch 1816a may connect transmission driver 1813a to piezoelectric element 1806a such that a signal is transmitted to the top electrode of piezoelectric element 1806a. During the receive (Rx) mode / process, switch 1816a may connect amplifier 1811a to piezoelectric element 1806a such that a signal is transmitted from the top electrode of piezoelectric element 1806a to amplifier 1811a.

[0122] Note that transmission driver 1813a may include various electrical components. However, for simplicity, transmission driver 1813a is represented by one driver. However, it should be apparent to those skilled in the art that the transmission driver may include more complex drivers with multiple functions. In FIG. 18A, only one amplifier 1811a is shown, but electrical components for processing received signals may be connected to amplifier 1811a. In an embodiment, amplifier 1811a may be a low noise amplifier (LNA). In an embodiment, circuit 1842n may have the same or a similar structure as circuit 184 2a.

[0123] In an embodiment, all DC biases (X) 1832a - 1832n may be connected to the same DC bias or ground, i.e., all of conductors (X) 1810a - 1810 n may be connected to a single DC bias or ground. Similarly, all DC biases (X) 1834a - 1834n may be connected to the same DC bias or different DC biases i.e., all of conductors (T) 1812a - 1812n may be connected to a single DC bias or ground.

[0124] In an embodiment, conductors (X, T, and O) 1810, 1812, and 1814 may be connected to the ASIC chip 1804 using an interconnect technology, such as copper pillar interconnects or bumps (e.g., 1882 in FIG. 18B), as indicated by arrow 1880. In an embodiment, circuit components within the ASIC chip 1804 may communicate with the outside of the ASIC chip 1804 using interconnects 1830. In an embodiment, the interconnects 1830 may be implemented using bonding wires from pads on the ASIC chip 1804 to another pad outside the ASIC chip. In an embodiment, in addition to wire bonding pads, other types of interconnects, such as bump pads or redistribution bumps, on the ASIC chip 1804 may be used.

[0125] In an embodiment, the LNA 1811 included in the circuit 1842 may be implemented outside the ASIC chip 1804, such as part of a receive analog front end (AFE). In an embodiment, the LNA may be present within the ASIC chip 1804, and another LNA and a programmable gain amplifier (PGA) may be present within the AFE. The gain of each LNA 1811 may be programmed in real time, allowing the LNA to be part of the time gain compensation function (TGC) required for the imager. ction)(TGC).

[0126] In an embodiment, the LNA 1811 may be constructed using low voltage transistor technology. Often, when exposed to the high transmission voltages required by conventional transducers, they can be damaged. Thus, in conventional systems, high-voltage transmit-receive switching switches are used to isolate the high transmission voltage from the low-voltage receiving circuits. Such switches are large and expensive, use a high-voltage (HV) process, and degrade the signal sent to the LNA . In contrast, in embodiments, low voltages may be used, and thus the high-voltage components of conventional systems may no longer be required. Also, in embodiments, by eliminating the conventional HV switch, the performance degradation caused by the conventional HV switch can be avoided.

[0127] In an embodiment, the piezoelectric element 1806 may be connected to the LNA 1811 by the switch 1816 during the receive mode. The LNA 1811 can convert the charge in the piezoelectric element 1806 generated by the reflected pressure wave that applies pressure to the piezoelectric element into a low-noise amplified voltage signal. The signal-to-noise ratio of the received signal can be one of the important factors determining the quality of the reconstructed image. Thus, it is desirable to reduce the inherent noise in the LNA itself. In an embodiment, the noise may be reduced by increasing the mutual conductance of the input stage of the LNA 1811, such as by using a larger current in the input stage. Increasing the current may cause an increase in power dissipation and heat. In an embodiment, the pMUT 1806 may be operated at a low voltage and may be close to the ASIC chip 1804. Thus, the power saved by the low-voltage pMUT 1806 may be used to lower the noise in the LNA 1811 for a given acceptable overall temperature rise compared to a conventional transducer operating at a high voltage.

[0128] FIG. 18B shows a schematic view of an imaging assembly 1850 according to an embodiment of the present disclosure. In an embodiment, the transceiver substrate 1852 and the ASIC chip 1854 may be the same as the transceiver substrate 1802 and the ASIC chip 1804, respectively. In a conventional system, an electronic circuit for driving a piezoelectric transducer is typically located far from the piezoelectric transducer and connected to the piezoelectric transducer using a coaxial cable. Generally, a coaxial cable increases parasitic loads such as additional capacitance to the electronic circuit, and the additional capacitance causes losses in important performance parameters such as increased noise and signal power loss. In contrast, as shown in FIG. 18B, the transmission driver or drivers (or equivalent circuits) 1862a-1862n may be directly connected to the piezoelectric elements (or equivalent pixels) 1856a-1856n+i using a low-impedance three-dimensional (3D) interconnect mechanism such as a Cu pillar or a solder bump 1882 (indicated by arrow 1880), or a wafer bond or a similar approach or a combination of such techniques. In an embodiment, when the transceiver substrate 1852 is integrated with the ASIC chip 1854, the circuit 1862 may be located less than 100 μm (or so) away from the piezoelectric element 1856 in the vertical direction. In an embodiment, any conventional device for impedance matching between the drive circuit 1862 and the piezoelectric element 1856 may not be required, further simplifying the design of the imaging assembly 1800 and improving power efficiency. The impedance of the circuit 1862 may be designed to match the requirements of the piezoelectric element 1856.

[0129] In an embodiment, in FIG. 18A, each of the piezoelectric elements 1806a-1806n may be electrically connected to a corresponding one of the circuits 1842a-1842n located within the ASIC chip 1804. In an embodiment, this configuration may allow the imager to generate a three-dimensional image. Similarly, in FIG. 18B, each of the piezoelectric elements 1856a-1856m may have three leads represented by X, T, and O. Each of the piezoelectric elements The leads therefrom may be electrically connected to a corresponding one of circuits 1862a - 1862m located within the ASIC chip 1854 by the interconnection means 1882. Further, in an embodiment, lines of piezoelectric elements such as 1856n + 1 - 1856n + i may be electrically coupled to a single common circuit 1862n. In an embodiment, the transmission driver circuit 1862n may be implemented with a single transmission driver. In an alternative embodiment, the transmission driver circuit 1862n may be implemented with a multi - level driver to facilitate various imaging modes.

[0130] It should be apparent to those skilled in the art that the ASIC chip 1854 may have any suitable number of circuits similar to the circuit 1862n. In an embodiment, the control unit 1892 may have the function of configuring piezoelectric elements horizontally or vertically in a two - dimensional pixel array, configuring their lengths, and setting them to transmit or receive or polling mode or idle mode. In an embodiment, the control unit 1892 may execute a polling process after the transceiver substrate 1852 is combined with the ASIC chip 1854 by the three - dimensional integration technology 1882. In an embodiment, the transmission driver circuit 1843 may be implemented with a multi - level drive as shown in FIG. 34, where the transmission driver output may have more than two output levels. FIG. 34 shows an embodiment where the output levels may be 0V or 6V or 12V. It is understood that these voltages may be different, for example, - 5V, 0V and + 5V. The transmission driver may also be a two - level driver with a drive signal as shown in FIG. 33.

[0131] In an embodiment, the lead wires 1882a - 1882n are the electrodes of the piezoelectric element 1856 (O It may be a signal conductor used to apply a pulse to (). Similarly, leads 1884a to 1884n, 1886a to 1886n, and 1888a to 1888n may be used to communicate signals with the piezoelectric elements 1856a to 1856n+i. Note that other suitable numbers of leads may be used to communicate signals / data with the imaging assembly 1800.

[0132] In an embodiment, each of lead (X) 1886 and lead (T) 1888 may be connected to a ground or DC bias terminal. In an embodiment, the digital control lead 1894 may be a digital control bus and may include one or more leads required to control and address various functions within the imaging assembly 1850. These leads may use a communication protocol such as, for example, a Serial Peripheral Interface (SPI) or other protocol to allow the programmability of the ASIC chip 1854.

[0133] In an embodiment, the piezoelectric element 1806 (or 1856) and the control electronics / circuit 1842 (or 1862) may be formed on the same semiconductor wafer. In an alternative embodiment, the transceiver substrate 1802 (or 1852) and the ASIC chip 1804 (or 1854) may be separately manufactured by a 3D interconnect technology such as a metal interconnect technology using bumps 1882 and combined with each other. In an embodiment, the interconnect technology can eliminate the low yield multiplication effect, thereby reducing the manufacturing cost and maximizing the yields of the various components independently.

[0134] In an embodiment, leads 1862a to 1862n are the electrodes (O) of the piezoelectric element 1806 It may be a signal conductor used to apply a pulse to (0). Similarly, lead wires 1864a to 1864n, 1866a to 1866n, and 1868a to 1868n may be used to communicate signals with the piezoelectric elements 1806a to 1806n. Note that other suitable numbers of lead wires may be used to communicate signals / data with the imaging assembly 1800.

[0135] As discussed above, the LNA 1811 may operate in a charge sensing mode and may have a programmable gain that can be configured in real time to provide gain compensation. In an embodiment, as discussed in connection with FIG. 3B, one or more temperature sensors may be installed within the imager 120. In an embodiment, the ASIC receives temperature data from the temperature sensor and uses the temperature data to adjust the imaging frame rate or the signal-to-noise ratio of the LNA 1 811.

[0136] FIG. 19A-1 shows a top view of the transceiver substrate 1902 and the ASIC chip 1906, and FIG. 19A-2 shows a side view of the imaging assembly 1901 according to an embodiment of the present disclosure. As shown, the imaging assembly 1901 may include a transceiver substrate 1902 interconnected to the ASIC chip 1906 by a suitable interconnect mechanism such as bumps. In the following, bumps are shown as the interconnect mechanism, but other suitable interconnect mechanisms may be used instead of bumps.

[0137] In an embodiment, each piezoelectric element 1904 may be a two-terminal piezoelectric element, where the piezoelectric element is symbolically represented by two electrodes O and X. In an embodiment, the circuit element 1908 may include an electrical component for driving the corresponding piezoelectric element 1904, where the circuit element 1908 is symbolically represented by a transmission driver. In an embodiment, the imaging element 1910 may include the piezoelectric element 1904 and the circuit element 1908, and the piezoelectric element 1904 may be electrically connected to the circuit element 1908 by two bumps.

[0138] FIG. 19B-1 shows a top view of the transceiver substrate 1911 and the ASIC chip 1913, and FIG. 19B-2 shows a side view of the imaging assembly 1915 according to an embodiment of the present disclosure. As shown, the imaging assembly 1915 may be similar to the imaging assembly 1901, but there is a difference in that two sub-piezoelectric elements are electrically coupled to two sub-circuit elements by three bumps. More specifically, the piezoelectric element 1912 includes two sub-piezoelectric elements, each sub-piezoelectric element may be a two-terminal piezoelectric element, and the X electrodes of the two sub-piezoelectric elements may be electrically coupled to each other. In an embodiment, each O electrode of the sub-piezoelectric element may be electrically coupled to the transmission driver of the corresponding sub- circuit element 1914, and the X electrodes of the two sub-piezoelectric elements may be electrically coupled to the common electrical terminal of the circuit element 1914. Thus, in each imaging element 1917, the piezoelectric element 1912 may be interconnected to the circuit element 1914 by three bumps. FIG. 19C shows a top view of the transceiver substrate 1920 and the ASIC chip 1924 according to an embodiment of the present disclosure. As shown, the transceiver substrate 1920 may be similar to the transceiver substrate 1902, but there is a difference in that three sub-piezoelectric elements are electrically coupled to three sub-circuit elements by four bumps. More specifically, the piezoelectric element 1922 includes three sub-piezoelectric elements, each sub-piezoelectric element may be a two-terminal piezoelectric element, and the X electrodes of the three sub-piezoelectric elements may be electrically coupled to each other. In an embodiment,

[0139] each O electrode of the sub-piezoelectric element may be electrically coupled to the transmission driver of the corresponding sub-circuit element, and the X electrodes of the three sub-piezoelectric elements may be electrically coupled to the common electrical terminal of the circuit element 1926. Thus, the piezoelectric element 1922 may be interconnected to the circuit element 1926 by four bumps.

[0140] ​​Note that the piezoelectric element may have more than two terminals. FIG. 19D shows a top view of a transceiver substrate 1930 and an ASIC chip 1934 according to an embodiment of the present disclosure. As shown, the transceiver substrate 1930 may be similar to the transceiver substrate 1902, but there is a difference that each piezoelectric element 1932 can be electrically coupled to the circuit element 1936 by three bumps. In an embodiment, the O electrode may be coupled to the transmission driver of the circuit element 1936 by a bump, and the X and T electrodes may be coupled to the circuit element 1936 by two bumps. There is a difference that it can be electrically coupled. In an embodiment, the O electrode may be coupled to the transmission driver of the circuit element 1936, and the X and T electrodes may be coupled to the circuit element 1936 by two bumps.

[0141] FIG. 19E shows a top view of a transceiver substrate 1940 and an ASIC chip 1944 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1942 may include two sub-piezoelectric elements, each sub-piezoelectric element may be a three-terminal piezoelectric element, and the X electrodes of the two sub-piezoelectric elements may be electrically coupled to each other. In an embodiment, each O electrode of the sub-piezoelectric element may be electrically coupled to the transmission driver of the corresponding sub-circuit element by a bump and the X electrodes of the two sub-piezoelectric elements may be electrically coupled to the circuit element 1946 by bumps and each T electrode of the sub-piezoelectric element may be electrically coupled to the circuit element 1946 by a bump In this way, the piezoelectric element 1942 may be interconnected to the circuit element 1946 by five bumps.

[0142] FIG. 19F shows a top view of a transceiver substrate 1950 and an ASIC chip 1954 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1952 may include two sub-piezoelectric elements, each sub-piezoelectric element may be a three-terminal piezoelectric element, the X electrodes of the two sub-piezoelectric elements may be electrically coupled to each other, and the T electrodes of the two sub-piezoelectric elements may be electrically coupled to each other. In an embodiment, each O electrode of the sub-piezoelectric element is a bump It may be electrically coupled to the transmission driver of the corresponding sub-circuit element by P, and the X electrodes of the two sub-piezoelectric elements may be electrically coupled to the circuit element 1956 by bumps. Also, the T electrodes of the two sub-piezoelectric elements may be electrically coupled to the circuit element 1956 by bumps and may be. In this way, the piezoelectric element 1952 may be interconnected to the circuit element 1956 by four bumps.

[0143] FIG. 19G shows a top view of a transceiver substrate 1960 and an ASIC chip 1964 according to an embodiment of the present disclosure. As shown, the piezoelectric element 1962 may include two sub-piezoelectric elements, each sub-piezoelectric element may be a three-terminal piezoelectric element, the O electrodes of the two sub-piezoelectric elements may be electrically coupled to each other, and the X electrodes of the two sub-piezoelectric elements may be electrically coupled to each other, and the T electrodes of the two sub-piezoelectric elements may be electrically coupled to each other. In this way, the piezoelectric element 1962 may be interconnected to the circuit element 1966 by three bumps.

[0144] FIG. 20 shows a schematic diagram of an m×n array 2000 of piezoelectric elements 2002-11 to 2002-mn according to an embodiment of the present disclosure. As shown, each piezoelectric element may be a two-terminal piezoelectric element (such as the piezoelectric element 900 in FIG. 9), and has an electrode (O) (such as 200 4-11) electrically coupled to a conductor (O) and an electrode (X) electrically connected to ground or a DC bias voltage via a common conductor (X) 2007 and may be. In an embodiment, each signal conductor (O) may be independently managed by a circuit element (such as 1908) In an embodiment, each conductor (O) (for example, 20 (04 - mn) may be electrically coupled to the transmission driver of the circuit element, and all X electrodes (2006 - 11 to 2006 - mn) of the piezoelectric element array may be connected to the common conductor (X) 2007. In an embodiment, the array 2000 is disposed on the transceiver substrate as discussed in relation to FIGS. 19A - 19G and may be electrically coupled to the ASIC chip by an interconnect mechanism such as m×n + 1 bumps. and thus may be electrically coupled to the ASIC chip. More specifically, the m×n conductors (O) 2 004 - 2004 - mn may be coupled to the m×n transmission drivers of the ASIC chip by m×n bumps, and the common conductor (X) 2007 may be coupled to the ASIC chip by one bump. In an embodiment, such an exemplary configuration described herein is used to perform 3D imaging, where each piezoelectric element including at least one sub - piezoelectric element can provide unique information in the array. In an embodiment, each piezoelectric element has one or more membranes and can vibrate at multiple modes and frequencies of the membranes. In an embodiment, each piezoelectric element 2002 may be driven by pulses having the voltage profiles 3300 and 3400 of FIGS. 33 and 34.

[0145] In an embodiment, the O electrodes of each column (e.g., 2003 - 11 to 2003 - m1) may be electrically coupled to a common conductor. For example, the circuit elements within the ASIC chip may be electronically controlled such that the O electrodes of each column are electrically coupled to each other. Such a configuration in which the O electrodes of each column can receive the same electrical pulse through a common transmission driver or by multiple drivers having the same electrical driving signal during the transmission mode. Similarly, the O electrodes of each column can simultaneously transmit the charge to a common amplifier during the reception mode. In other words, the piezoelectric elements of each column may be operated as a line unit (or equivalent, a line element).

[0146] FIG. 21 shows a schematic diagram of an n×n array 2100 of piezoelectric elements 2102-11 to 2012-mn according to an embodiment of the present disclosure. As shown, each piezoelectric element may be a three-terminal piezoelectric element and may include electrodes O, X, and T. In an embodiment, the X electrodes (e.g., X11, X21, …, Xm1) may be connected in series for each column, and all of the X electrodes (X11 to Xmn) may be electrically coupled to a common conductor (X) 2106. The T electrodes (e.g., T11, T21, …, Tm1) may be connected in series for each column, and all of the T electrodes (T11 to Tmn) may be electrically coupled to a common conductor (T) 2108. Columns of elements such as 2102-11, 2102- 21 to 2102-m1, when connected together as described in the embodiment, constitute line elements or columns. In an embodiment, each of the O electrodes 2103-11 to 210 3-mn may be electrically coupled to a transmission driver of a corresponding circuit element within the ASIC chip via one of the conductors O11 to Omn. In an embodiment, the array 2100 is disposed on a transceiver substrate and may be electrically coupled to the ASIC chip by an interconnect mechanism such as m×n+2 bumps ..

[0147] In an embodiment, the O electrodes of each column (e.g., 2103-11 to 2103-m1) may be electrically coupled to a common conductor. In such a configuration, the O electrodes of each column can receive the same electrical pulse through a common transmission driver during the transmission mode. Similarly, the O electrodes of each column can simultaneously transmit charge to a common amplifier during the reception mode. In other words, the piezoelectric elements of each column operate as line units. In an embodiment, each of the O electrodes within a column may be connected to a dedicated transmission driver, where within the column .. The input signals of the transmission driver for all elements are the same, thus capable of generating substantially the same transmission drive output that should appear on all piezoelectric elements during the transmission operation. Such line elements are electronically controlled for each element since each element has its own transmission driver. This has advantages when driving large capacitive line elements. Each element has a smaller capacitance and can minimize the timing delay for the elements in a column. In an embodiment, in the reception mode, the charge from all elements within a column can be sensed by connecting it to the LNA subsequently. This is similar to what is done by 2D imaging. For 3D imaging, during the reception mode operation, by connecting the O electrode of each element to the LNA, the charge for each element is sensed.

[0148] FIG. 22 shows a schematic diagram of an m×n array 2200 of piezoelectric elements 2202-11 to 2202-mn according to an embodiment of the present disclosure. As shown, the array 2200 may be similar to the array 2100, but there is a difference that the X electrodes (e.g., X12 to Xm2) within a column may be connected to a common conductor (e.g., , 2206-1), and the T electrodes (e.g., T12 to Tm2) within a column may be connected to a common conductor ( e.g., 2208-1). Thus, the X electrodes (or T electrodes) within the same column may have the same voltage potential during operation. In an embodiment , each of the O electrodes may be electrically coupled to the corresponding circuit element's transmission driver within the ASIC chip via one of the conductors O11 to Omn. In an embodiment, the array 2200 may be disposed on a transceiver substrate and electrically coupled to the ASIC chip by an interconnect mechanism such as m×n+2n bumps.

[0149] Compared with array 2100, array 2200 can use more bumps for connecting the T electrodes and the X electrodes to the ASIC chip. Generally, an increase in the number of connections for T and X between the ASIC chip and the piezoelectric array can reduce the impedance of the X and T conductors when connected in parallel to a ground or DC bias source, and can reduce crosstalk. Crosstalk refers to the coupling of signals from an imaging element to other elements, which may cause interference and degrade image quality. Spurious electrical coupling can occur when any voltage drop due to the current flowing through the X and T lines appears around a piezoelectric element that ideally should not be exposed to that voltage. In an embodiment, when the piezoelectric element is neither transmitting nor receiving under electronic control, the X, T, and O electrodes may be locally short-circuited. Alternatively, the idle electrode may ground the O electrode, the X electrode may be connected to other X electrodes in the array, and the T electrode may remain connected to other T electrodes in the array.

[0150] FIG. 23 shows a schematic diagram of an m×n array 2300 of piezoelectric elements 2302-11 to 2302-mn according to an embodiment of the present disclosure. As shown, the array 2300 may be similar to the array 2100, and each piezoelectric element may be a five-terminal piezoelectric element, that is, each piezoelectric element may include one lower electrode (O) and four upper electrodes (two X electrodes and two T electrodes). In an embodiment, the two X electrodes of each piezoelectric element may be connected in series for each column, and all of the 2m×n X electrodes may be electrically coupled to a common conductor (X) 2306. Similarly, the two T electrodes of each piezoelectric element may be connected in series for each column, and all of the 2m×n T electrodes may be electrically coupled to a common conductor (T) 2308. In an embodiment, each of the O electrodes may be electrically coupled to a transmission driver of a corresponding circuit element in the ASIC chip via one of conductors O11 to Omn. In an embodiment, the array 2300 is disposed on a transceiver substrate and has m×n+2 pieces or the like. It may be electrically coupled to the ASIC chip by an interconnect mechanism such as bumps.

[0151] FIG. 24 shows a schematic diagram of an m×n array 2400 of piezoelectric elements 2402-11 to 2402-mn according to an embodiment of the present disclosure. As shown, the array 2400 may be similar to the array 2200, but each piezoelectric element may be a five-terminal piezoelectric element: one lower electrode (O) and and there is a difference that it may be four upper electrodes (two X electrodes and two T electrodes). In an embodiment, the two X electrodes of each piezoelectric element may be electrically connected in a column-by-column direction to a conductor (for example, 2406-1), and the two T electrodes of each piezoelectric element may be electrically connected in a column-by-column direction to a common conductor (for example, 2408-1). In an embodiment, each of the O electrodes may be electrically coupled to the transmission driver of the corresponding circuit element in the ASIC chip via one of the conductors O11 to Omn. In an embodiment, the array 2400 may be disposed on a transceiver substrate and may be electrically coupled to the ASIC chip by an interconnect mechanism such as m×n+2n bumps.

[0152] FIG. 25 shows a schematic diagram of an m×n array 2500 of piezoelectric elements 2502-11 to 2502-mn according to an embodiment of the present disclosure. As shown, the array 2500 may be similar to the array 2100 in that each piezoelectric element may have one lower electrode (O) and two upper electrodes (T), but there is a difference that all of the two upper electrodes (T) of the piezoelectric elements (for example, 2502-11 to 2502-m1) along the column may be electrically connected to a common conductor (for example, 2508- 1). In an embodiment, each of the O electrodes may be electrically coupled to the transmission driver of the corresponding circuit element in the ASIC chip via one of the conductors O11 to Omn. In an embodiment, the array 2500 may be disposed on a transceiver substrate and may be electrically coupled to the ASIC chip by an interconnect mechanism such as m×n+n bumps. ​​​ may be coupled to.

[0153] FIG. 26 shows a schematic view of an m×n array 2600 of piezoelectric elements 2602-11 to 2602-mn according to an embodiment of the present disclosure. As shown, the array 2600 may have electrical connections similar to those of the array 2100, that is, all of the X electrodes in the piezoelectric elements may be electrically coupled to the common conductor 2606, and all of the T electrodes in the piezoelectric elements may be electrically coupled to the common conductor 2608. The array 2600 may be different from the array 2100 in that the upper electrodes (X, T) of a certain piezoelectric element (e.g., 2602-11) may have the same or different geometric shapes as the upper electrodes (X, T) of another piezoelectric element (e.g., 2602-21).

[0154] Regarding the piezoelectric arrays 2000 to 2500, the piezoelectric elements of each piezoelectric array may be the same as or different from each other. For example, the projected areas of the two upper electrodes of one piezoelectric element 2202-11 may have the same or different shapes as the projected areas of the two upper electrodes of another piezoelectric element 2202-n1.

[0155] FIG. 27 shows a schematic view of an m×n array 2700 of piezoelectric elements 2702-11 to 2702-mn according to an embodiment of the present disclosure. As shown, each piezoelectric element may include two signal electrodes (O) and one common electrode (X). In an embodiment, each signal electrode (O) It may be electrically coupled to the transmission driver of the corresponding circuit element of the ASIC chip. For example, the piezoelectric element 2702-11 may include two signal conductors O111 and O112 that can be electrically coupled to two circuit elements in the ASIC chip respectively, and each signal electrode may generate charge during the reception mode. In an embodiment, the array 2700 may be disposed on a transceiver substrate and may be electrically coupled to the ASIC chip by an interconnection mechanism such as 2m×n + 1 bumps. In an embodiment, all T electrodes in the array 2700 may be electrically coupled to ground or a DC bias voltage via a common conductor (T) 2708.

[0156] In an embodiment, the signal conductor (O) in the array of FIGS. 20 to 27 may be electrically coupled to a circuit element, where the circuit element may include a transistor switch similar to the switch 1816 in FIG. 18A, that is, the switch may toggle between a transmission driver and an amplifier between the transmission mode and the reception mode such that the O electrode generates a pressure wave during the transmission mode and may generate charge during the reception mode.

[0157] FIG. 28 shows an exemplary embodiment of an imaging system 2800 according to an embodiment of the present disclosure. As shown, the imaging system 2800 may include an array of piezoelectric elements 2802-11 to 2802-mn and circuit elements for controlling / communicating with the array. In an embodiment, each of the piezoelectric elements 2802-11 to 2802-mn may include three electrodes: a first and a second signal (O) electrode and a T electrode. (For illustration, the first and second O electrodes in each piezoelectric element refer to the left and right O electrodes of each piezoelectric element in FIG. 28.) In an embodiment, all of the T electrodes in the array 2800 may be electrically coupled to ground or a DC bias voltage via a conductor (T) 2808. In an In a configuration, the first O electrode of the piezoelectric elements in a column may be electrically coupled to a common conductor (e.g., O11), and the second O electrode of the piezoelectric elements in the same column may be electrically coupled to another common conductor (e.g., O12). In an embodiment, during the receive mode, each of the first and second signal O electrodes may generate charge that can be processed by a corresponding circuit.

[0158] In an embodiment, the first set of conductors O11, O21, …, On1 may each be electrically coupled to amplifiers 2810-1 ~2810-n, where the charge appearing in the column of the first O electrodes may be transmitted to the corresponding amplifier via one of the O conductors. In an embodiment , the second set of conductors O12, O22, …, On2 may each be electrically coupled to switches 2812-1~2812-n . In an embodiment, each switch (e.g., 2812-1) may be connected to a transmit driver (e.g., , 2816-1) during the transmit mode / process so that a signal pulse can be transmitted to the column of the second O electrodes in the piezoelectric elements (e.g., 2801-11~2802-m1). In an embodiment, each switch (e.g., 2812-1) may be connected to a signal amplifier (e.g., 2814-1) during the receive mode / process, whereby the charge appearing in the column of the second O electrodes in the piezoelectric elements (e.g., 2801-11~2802-m1) can be transmitted to the amplifier. In an embodiment, the piezoelectric elements 2802-11~2802-mn may be disposed within a transceiver substrate, while the switches 2812-1~2812-n, transmit drivers 2816-1~2816-n, and amplifiers 2810-1~2810-n and 2814-1~2814-n may be disposed within an ASIC chip, and the transceiver substrate may be electrically coupled to the ASIC chip by 2n + 1 bumps.

[0159] In an embodiment, the column of the first electrodes is electrically coupled to a common conductor (e.g., O11) Alternatively, the columns of the second electrodes may be electrically coupled to another common conductor (e.g., O12). In this way, in an embodiment, the imaging system 2800 may operate as a line imager, i.e., each of the first set of conductors O11 to On2 may operate as a transmitting unit and / or a receiving unit during operation. As discussed above, during the receiving mode, the charge appearing in the column of the first O electrodes connected to a conductor (e.g., O11) may be transmitted to an amplifier (e.g., 2810-1) which may be a low-noise amplifier. Next, the amplifier may amplify the charge signal and convert the charge signal into an output voltage. In this way, each column of the first O electrodes can operate as a receiving line imager. In an embodiment, during the receiving mode, the charge appearing in the column of the second O electrodes connected to a conductor (e.g., O12) may be transmitted via a switch (e.g., 2812-1) to a signal amplifier (e.g., 2814-1) which may be a low-noise amplifier. Next, the amplifier can amplify the charge signal and convert the charge signal into an output voltage. In this way, each column of the second O electrodes can operate as a receiving line imager. In an embodiment, during the transmitting mode, an electrical signal pulse may be transmitted from a transmitting driver (e.g., 2816-1) via a switch (e.g., 2812-1) to the column of the second O electrodes connected to a conductor (e.g., O12), such that the set of the second O electrodes can generate a pressure wave. In this way, each column of the second O electrodes may operate as a transmitting line unit.

[0160] In an embodiment, the switch 2812, which may be a transistor switch, may be set to a neutral position during the receiving mode (i.e., those switches are not coupled to either the transmitting driver or the amplifier). In such a case, only the second set of conductors O12, O22, …, On2 may operate during the receiving mode.

[0161] In an embodiment, a transmission driver (e.g., 2816-1) may send a signal to a column of piezoelectric elements (e.g., 2802-11 to 2802-m1) via a conductor (O12). At the same time, an amplifier (e.g., 2810-1) may receive a charge signal from the same column of piezoelectric elements (e.g., 2802-11 to 2802-m1). In such a case, each piezoelectric element (e.g., 2802-11) within the column may receive a signal from a transmission driver (e.g., 2816-1) through one conductor (e.g., O12) and at the same time send a charge signal to an amplifier (e.g., 2810-1) through another conductor (e.g., O11). That is, the imaging system 2800 may perform simultaneous transmission and reception modes. This simultaneous operation of the transmission and reception modes can be very advantageous in continuous mode Doppler imaging where high blood flow velocities can be imaged, as compared to pulsed Doppler imaging. In an embodiment, a line unit, which refers to a column of O electrodes electrically coupled to a common conductor, can operate as a transmission unit, a reception unit, or both. For example, during the transmission mode, an electrical signal is sequentially sent to conductors O12, O22,..., On2, and various line elements sequentially generate pressure waves. During the reception mode, the reflected pressure waves are processed to generate a two-dimensional image of the target organ in combination. In another example, during the transmission mode, an electrical drive signal may be simultaneously sent to conductors O12, O22,..., On2. At the same time, the reflected pressure waves may be processed using the charges generated from conductors O11, O12 to On1, and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode. and at the same time send a charge signal to an amplifier (e.g., 2810-1) through another conductor (e.g., O11). That is, the imaging system 2800 may perform simultaneous transmission and reception modes. This simultaneous operation of the transmission and reception modes can be very advantageous in continuous mode Doppler imaging where high blood flow velocities can be imaged, as compared to pulsed Doppler imaging. In an embodiment, a line unit, which refers to a column of O electrodes electrically coupled to a common conductor, can operate as a transmission unit, a reception unit, or both. For example, during the transmission mode, an electrical signal is sequentially sent to conductors O12, O22,..., On2, and various line elements sequentially generate pressure waves. During the reception mode, the reflected pressure waves are processed to generate a two-dimensional image of the target organ in combination. In another example, during the transmission mode, an electrical drive signal may be simultaneously sent to conductors O12, O22,..., On2. At the same time, the reflected pressure waves may be processed using the charges generated from conductors O11, O12 to On1, and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode.

[0162] In an embodiment, a line unit, which refers to a column of O electrodes electrically coupled to a common conductor, can operate as a transmission unit, a reception unit, or both. For example, during the transmission mode, an electrical signal is sequentially sent to conductors O12, O22,..., On2, and various line elements sequentially generate pressure waves. During the reception mode, the reflected pressure waves are processed to generate a two-dimensional image of the target organ in combination. In another example, during the transmission mode, an electrical drive signal may be simultaneously sent to conductors O12, O22,..., On2. At the same time, the reflected pressure waves may be processed using the charges generated from conductors O11, O12 to On1, and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode. For example, during the transmission mode, an electrical signal is sequentially sent to conductors O12, O22,..., On2, and various line elements sequentially generate pressure waves. During the reception mode, the reflected pressure waves are processed to generate a two-dimensional image of the target organ in combination. In another example, during the transmission mode, an electrical drive signal may be simultaneously sent to conductors O12, O22,..., On2. At the same time, the reflected pressure waves may be processed using the charges generated from conductors O11, O12 to On1, and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode. and various line elements sequentially generate pressure waves. During the reception mode, the reflected pressure waves are processed to generate a two-dimensional image of the target organ in combination. In another example, during the transmission mode, an electrical drive signal may be simultaneously sent to conductors O12, O22,..., On2. At the same time, the reflected pressure waves may be processed using the charges generated from conductors O11, O12 to On1, and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode. and at the same time, the reflected pressure waves may be processed using the charges generated from conductors O11, O12 to On1, and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode. and ultrasonic transmission and reception may be performed simultaneously to form a two-dimensional image. Conductors O12 to On2 may also be used to receive charges from the piezoelectric line elements in the reception operation mode.

[0163] FIG. 29 shows an exemplary embodiment of an imaging system 2900 according to an embodiment of the present disclosure. As shown, the imaging system 2900 includes an array of piezoelectric elements 2902-11 to 2902-mn, and each piezoelectric element may include first and second signal (O) electrodes and a T electrode. In an embodiment, all of the T electrodes in the array may be electrically coupled to a single common conductor (T) 2908, and each row of the first O electrodes may be electrically connected to one of conductors O1 to Om, and each column of the second O conductors may be electrically connected to a switch 2912 via one of conductors O12 to On2. In an embodiment, each of switches 2912-1 to 2912-n may toggle between a transmission driver (e.g., 2916-1) and an amplifier (e.g., 2914-1) that may be a low-noise amplifier. In an embodiment, each of conductors O1 to On may be connected to one of amplifiers 2910-1 to 2910-m that may be low-noise amplifiers. electrically connected, and each column of the second O conductors may be via one of conductors O12 to On2 electrically connected to a switch 2912. In an embodiment, each of switches 2912-1 to 2912-n may toggle between a transmission driver (e.g., 2916-1) and an amplifier (e.g., 2914-1) that may be a low-noise amplifier. In an embodiment, each of conductors O1 to On may be connected to one of amplifiers 2910-1 to 2910-m that may be low-noise amplifiers.

[0164] In an embodiment, during the transmission mode, the signal may be transmitted from a transmission driver (e.g., 2916-1) via a conductor (e.g., O12) to a column of the second O electrodes so that a column of piezoelectric elements can generate a pressure wave as a line unit. During the transmission mode, each switch (e.g., 2912-1) may be toggled to a corresponding transmission driver (e.g., 2916-1).

[0165] In an embodiment, the imaging system 2900 may process the reflected pressure wave in two different ways. In the first way, amplifiers 2910-1 to 2910-n may receive a charge signal from the first O electrodes, that is, each amplifier receives a signal from a row of the first O electrodes and may receive a charge signal, that is, each amplifier receives a signal from a row of the first O electrodes This is also acceptable. This method allows for two-plane imaging / mode, where for a two-dimensional image, the two-plane image can provide orthogonal viewpoints. Also, this method can provide more than just two-dimensional imaging capabilities. Two-plane imaging can be useful in many applications such as biopsies. Note that in this method, the transmission mode and the reception mode may be executed simultaneously. In a second method, each amplifier may receive a charge signal from the corresponding column of the second O electrodes and be toggled to amplifier 2914 by switch 2912. Switch 2912 may be toggled to amplifier 2914.

[0166] In an embodiment, a line unit, which refers to a column (or row) of O electrodes electrically coupled to an O conductor, may operate as a transmission unit or a reception unit, or both. In an embodiment, conductors O1 to Om are arranged in a direction orthogonal to conductors O12 to On2, and these directions are electronically programmable and electronically adjustable. For example, the gains of amplifiers 2910 and 2914 may be electronically adjustable if gain control leads are implemented within the amplifiers. In an embodiment, the length of each line element (i.e., the number of piezoelectric elements within each line element) may also be electronically adjusted. In an embodiment, this can be achieved by connecting all the signal electrodes of each piezoelectric element to the corresponding nodes of an ASIC chip. Here, the ASIC appropriately programs the connections between the signal electrodes of the elements to be connected to each other, the transmission driver, or the amplifier.

[0167] FIG. 30 shows an embodiment of a piezoelectric element 3000 coupled to a circuit element 3001 according to an embodiment of the present disclosure. As shown, the piezoelectric element 3000 may include a first sub-piezoelectric element 3021-1 and a second sub-piezoelectric element 3021-2. The piezoelectric element 3000 may be shared by the first and second sub-piezoelectric elements and may include a lower electrode (X) 3002 coupled to conductor (X) 3006. In an embodiment, the first sub-piezoelectric element 3021-1 is electrically coupled to an amplifier 3010 via a conductor 3008 for a signal (O). and may include a lower electrode (X) 3002 that is shared by the first and second sub-piezoelectric elements and coupled to conductor (X) 3006. In an embodiment, the first sub-piezoelectric element 3021-1 is electrically coupled to amplifier 3010 via conductor 3008 for signal (O). It may include the electrode 3003. In an embodiment, the second sub-piezoelectric element 3021-2 is a signal (O) electrode 300 that is electrically coupled to the switch 3014 via the conductor 3012 It may include 4.

[0168] In an embodiment, the circuit element 3001 may be electrically coupled to the piezoelectric element 3000 and may include two amplifiers 3010 and 3016 such as a low-noise amplifier, and a transmission driver 3018. In an embodiment, the switch 3014 has one end connected to the O electrode 3004 through the conductor 3012 and the other end that can toggle between the amplifier 3016 for the reception mode and the transmission driver 3018 for the transmission mode In an embodiment, the amplifier 3016 may be further amplified, filtered, and digitized the received signal and may be connected to other electronic circuits, but the amplifier is used to symbolically represent the electronic circuit. The transmission driver 3018 may be a multi-stage drive and may generate an output having two or more levels of signal transmission. The signal transmission can be unipolar or bipolar. In an embodiment, the transmission driver 3018 may include a switch that interconnects the input to the output of the driver under the electronic control of the driver, which is not explicitly shown in FIG. 30.

[0169] In an embodiment, the signal of the transmission driver 3018 may be pulse-width modulated (PWM) wherein a weighting function may be created for the transmitted ultrasonic signal by controlling the pulse width for each element. This may perform, for example, a windowing function in which the transmitted signal is weighted by a window function. In an embodiment, the weighting factor may be achieved by changing the duty cycle of the transmitted signal so as to be performed during the PWM signal transmission This type of operation may allow transmit apodization in which the side lobes of the radiated signal are significantly attenuated, allowing a higher quality image.

[0170] In an embodiment, the transceiver array may be disposed within a transceiver substrate, may include an n×n array of piezoelectric elements 3000, an n×n array of circuit elements 3001 may be disposed within an ASIC chip, and each piezoelectric element 3000 may be electrically coupled to a corresponding one of the n×n array of circuit elements 3001. In such a case, the transceiver substrate may be interconnected to the ASIC chip by 3n 2 bumps. In an embodiment , each column (or row) of the piezoelectric element array may operate as a line unit, as discussed in connection with FIGS. 28 and 29. For example, the same pulse may be applied simultaneously to a column of piezoelectric elements so that the columns of piezoelectric elements can generate pressure waves simultaneously. Each piezoelectric element 3000 of the n ×n array of piezoelectric elements may be coupled to a corresponding one of the circuit elements 3 001 of the n×n array of circuit elements. Note that

[0171] In an embodiment, the sub-piezoelectric element 3021-1 may be in a receive mode throughout the operation period, while the sub-piezoelectric element 3021-2 may be in either a transmit mode or a receive mode. In an embodiment, simultaneous operation of the transmit and receive modes may permit continuous mode Doppler imaging.

[0172] In an embodiment, when the transmit driver 3018 transmits a signal to the electrode 3004, the power level of the pressure wave generated by the sub-piezoelectric element 3021-2 may be changed by using pulse width modulation (PWM) signal transmission. This may be important, for example, when switching from B-mode to Doppler -mode imaging. The signal power transmitted to the human body may be long, and tissue damage may occur if the power level cannot be reduced. Typically in a conventional system, for B-mode and various Doppler-mode imaging Different high-speed tuning power supplies are used, and in two such cases, for example, in Doppler mode, the transmitted drive voltage is allowed to be different so as not to generate excessive power. Different from such a conventional system, in an embodiment, the power level can be changed by using a PWM signal for transmission without using a conventional high-speed tuning power supply. In the embodiment, a rapid switching between Doppler mode and B-mode imaging is desired for co-imaging these modes together. In an embodiment, the ground electrodes of the piezoelectric elements may be separated from each other and separately connected to ground. In an embodiment, this independent grounding can reduce noise and result in a faster tuning time. In an embodiment, the transmitted power may be reduced by reducing the height of the transmission train under electronic control. This also facilitates using the same power supply for both Doppler mode and B mode and can meet the power transmission requirements in each mode. This also allows co-imaging.

[0173] FIG. 31 shows a circuit 3100 for controlling a plurality of piezoelectric elements according to an embodiment of the present disclosure. In an embodiment, the circuit 3100 may be disposed within an ASIC chip, where a line (column or row) of piezoelectric elements disposed within a transceiver substrate and the ASIC chip may be interconnected to the transceiver substrate by bumps. As shown, the circuit 3100 may include an array of circuit elements 3140-1 to 3140-n, where each circuit element may communicate with the O electrode and the X electrode of the corresponding piezoelectric element.

[0174] As shown in FIG. 31, each circuit element (e.g., 3140-1) may include a first switch (e.g., 3102-1), a second switch (e.g., 3104-1), a third switch (e.g., 3106-1), and a transmission driver (e.g., 3108-1). The output from the transmission driver (e.g., 3108-1) may be sent to the O electrode of the piezoelectric element via a conductor (e.g., 3110-1). During the transmission mode, each circuit element may receive a transmission driver (drive) signal 3124 through conductor 3122. Each second switch (e.g., 3104-1), which may be a transistor switch controlled by control unit 3150, may be turned on to transmit signal 3124 to the transmission driver (e.g., 3108-1). (The electrical connections between control unit 3150 and other components within circuit 3100 are not shown in FIG. 31.) The transmission driver (e.g., 3108-1) performs logical decoding, level shifting, buffers the input signal, and transmits a transmission signal to the O electrode via a conductor (e.g., 3110-1). In an embodiment, during the transmission mode, the first switch (e.g., 3102-1) may be turned off.

[0175] In an embodiment, control unit 3150 may determine which piezoelectric elements need to be turned on during the transmission mode. If control unit 3150 determines not to turn on the second piezoelectric element, the first switch (e.g., 3102-2) and the second switch (e.g., 3104-2) may be turned off, while the third switch (e.g., 3106-2) may be turned on so that the O electrode and the X electrode have the same potential (i.e., so that a net zero-volt drive is applied to the piezoelectric layer). In an embodiment, the third switch 3106 may be optional.

[0176] In an embodiment, during the reception mode, the first switch (e.g., 3102-1) transmits the charge appearing at the O electrode to amplifier 3128 through conductors 3110-1 and 3120. It may be turned on so as to be possible. Next, the amplifier 3128 may receive the charge signal (or equivalently, the sensor signal) 3126 and amplify the sensor signal. The amplified signal may be further processed to generate an image. During the reception mode, the second switch (e.g., 3104-1) and the third switch (e.g., 3106-1) may be turned off so that the received signal is not interfered with. Note that the entire array of circuit elements 3140-1 to 3140-n may share a common amplifier 3128, simplifying the design of the circuit 3100. In an embodiment, the X electrodes of the piezoelectric elements may be electrically coupled to ground or a DC bias voltage via conductors 3112-1 to 3 112-n, where the conductors 3112-1 to 3112-n may be electrically coupled to a common conductor 3152.

[0177] In an embodiment, the circuit 3100 may be coupled to a column of the piezoelectric elements (e.g., 2002-11 to 2002-n1) of FIG. 20. In an embodiment, a plurality of circuits similar to the circuit 3100 may be coupled to a plurality of columns of the piezoelectric elements within the array of FIG. 20, and the conductor 3152 may be coupled to a common conductor (e.g., 2007 in FIG. 20). In an embodiment, the circuit 3100 may control the columns of the piezoelectric elements of FIGS. 20 to 27.

[0178] FIG. 32 shows a circuit 3200 for controlling a plurality of piezoelectric elements according to an embodiment of the present disclosure. In an embodiment, the circuit 3200 may be disposed within an ASIC chip, where a line (column or row) of piezoelectric elements disposed within a transceiver substrate and the ASIC chip may be interconnected to the transceiver substrate by bumps. As shown, the circuit 3200 may include an array of circuit elements 3240-1 to 3240-n, where each circuit element may communicate with the O, X, and T electrodes of a corresponding piezoelectric element.

[0179] As shown in FIG. 32, each circuit element (e.g., 3240-1) may include a first switch (e.g., 3202-1), a second switch (e.g., 3204-1), a third switch (e.g., 3206-1), a fourth switch (e.g., 3207-1), and a transmission driver (e.g., 3208-1). The output from the transmission driver (e.g., 3208-1) may be sent to the O electrode of the piezoelectric element via a conductor (e.g., 3210-1). During the transmission mode, each circuit element may receive a transmission driver (or drive) signal 3224 through conductor 3222. Each second switch (e.g., 3204-1), which may be a transistor switch controlled by control unit 3250, may be turned on to send signal 3224 to the transmission driver (e.g., 3208-1). (The electrical connections between control unit 3250 and other components within circuit 3200 are not shown in FIG. 32.) The transmission driver (e.g., 3208-1) may logically decode the signal, level-shift the signal, buffer the output signal, and send the transmission output signal to the O electrode via a conductor (e.g., 3210-1). In an embodiment, during the transmission mode, the first switch (e.g., 3202-1) may be turned off.

[0180] In an embodiment, control unit 3250 may determine which piezoelectric elements need to be turned on during the transmission mode. If control unit 3250 determines not to turn on the second piezoelectric element, the first switch (e.g., 3202-2) and the second switch (e.g., 3204-2) may be turned off, while the third switch (e.g., 3206-2) and the fourth switch (e.g., 3207-2) are connected to the O electrode and The Y (and T) electrodes may be turned on so that they have the same potential (i.e., so that zero-volt driving is applied to the piezoelectric layer). In an embodiment, the third and fourth switches (e.g., 3206-2 and 3207-2) may be optional. It is understood that three-level signal transmission and the transmission driver that performs it are not explicitly shown. Similarly, the connection to the XT conductor and switches such as 3206-2 and 3207-2 is shown in a simplified manner.

[0181] In an embodiment, during the reception mode, the first switch (e.g., 3202-1) may be turned on so that the charge appearing at the O electrode is transmitted to the amplifier 3228 via the conductors 3210-1 and 3220. Then, the amplifier 3228 may amplify the charge (or sensor ) signal 3226, and the amplified signal may be further processed to generate an image. During the reception mode, the second switch (e.g., 3204-1), the third switch (e.g., 3206-1), and the fourth switch (e.g., 3207-1) may be turned off so that the received signal is not interfered with.

[0182] Note that the entire array of circuit elements 3240-1 to 3240-n may share a common amplifier 3228, simplifying the design of the circuit 3200. In an embodiment, the X electrode of the piezoelectric element may be electrically coupled to ground or a DC bias voltage via conductors 3212-1 to 3212-n, where the conductors 3212-1 to 3212-n may be electrically coupled to a common conductor 3252. In an embodiment, the T electrode of the piezoelectric element may be electrically coupled to ground or a DC bias voltage via conductors 3 213-1 to 3213-n, where the conductors 3213-1 to 3213-n may be electrically coupled to a common conductor 3254.

[0183] In an embodiment, circuit 3200 may be coupled to a column of piezoelectric elements (e.g., 2102-11 to 2102-n1) in FIG. 21. In an embodiment, a plurality of circuits similar to circuit 3200 may be coupled to a plurality of columns of piezoelectric elements in the array of FIG. 21, and conductor 3252 may be coupled to a common conductor (e.g., 2106 in FIG. 20). Similarly, in an embodiment, conductor 3254 may be coupled to a common conductor (e.g., 2108 in FIG. 21). In an embodiment, circuit 3200 may control the columns of piezoelectric elements in FIGS. 20-27.

[0184] In FIGS. 22-32, conductors are used to electrically couple one electrode to another electrode. For example, electrodes 2006-11 to 2006-m1 are electrically coupled to conductor 2007. In an embodiment, the conductors in FIGS. 22-32 may be implemented in various ways. For example, a metal interconnect layer is deposited and patterned on a substrate on which the piezoelectric elements are disposed or on a different substrate connected to the substrate, such as an ASIC.

[0185] FIGS. 33 and 34 show exemplary waveforms 3300 and 3400 for driving piezoelectric elements during a transmit mode according to embodiments of the present disclosure. Generally, piezoelectric materials can be vulnerable to damage caused by dielectric aging, and aging can be slowed or avoided by using a unipolar drive signal. Waveforms 3300 and 3400 represent the voltage potential between the O electrode and the X electrode and / or between the O electrode and the T electrode. As shown, these waveforms may be of a unipolar nature, either a two-level step waveform 3300 (i.e., transmit drivers such as 2812, 2912, 3018, 3108, 3208, etc. are unipolar transmit drivers) or a multi-level (e.g., three-level) step waveform 3400. The actual voltage amplitude can typically vary from 1.8V to 12.6V and can change. In an embodiment, a multi-step waveform 3400 or a waveform with more steps can reduce heating in the piezoelectric element and has advantages for use during certain imaging modes such as Doppler or harmonic imaging.

[0186] In an embodiment, the frequencies of the pulses in waveforms 3300 and 3400 may vary according to the nature of the signal required, and need to include the frequencies to which the membrane underlying the pMUT responds. In an embodiment, the waveform may also be a complex signal such as a linearly or non-linearly frequency-modulated chirp signal, or other encoded signal using a Golay code.

[0187] In an embodiment, the circuit for driving the piezoelectric element may be further designed such that the shape of the transmission output from the underlying membrane can be symmetric. In an embodiment, for each signal pulse within waveform 3300 (or 3400), the rising edge of the pulse may be substantially symmetric with respect to the center of the pulse to the falling edge of the pulse. This symmetry reduces the harmonic content of the transmitted signal, particularly the second harmonic and other even-order harmonic signals. In an embodiment, the signal pulses within waveform 3300 (or 3400) may be pulse-width modulation (PWM) signals.

[0188] FIG. 35 shows a transmission drive signal waveform according to an embodiment of the present disclosure. As shown, the signal 3500 from the transmission driver may be symmetric and bipolar, that is, the magnitude (H1) and width (W1) of the peak maximum voltage are the same as the magnitude (H2) and width (W2) of the peak minimum voltage. Also, the slope of the rising edge 3502 is the same as the slope of the falling edge 3504. Further, the rise time W3 is the same as the fall time W4, where the fall time W4 refers to the time interval between the fall start point and the reference voltage. Further, the rising edge 3506 has the same slope as the rising edge 3502.

[0189] During the transmission operation, a transmission driver, such as 3018 in FIG. 30, may be driven by an electrical waveform as shown in FIGS. 33 to 34. FIG. 36 shows the output signals of various circuits within the imaging assembly according to an embodiment of the present disclosure. In the embodiment, waveform 3602 may be an output signal from a transmission driver, such as 3018, and may be transmitted to a piezoelectric element, such as 3000. In the embodiment, since the piezoelectric element may have a specific bandwidth, it may output a sine wave output 3604 at its resonance frequency. Connected to the O electrode of the piezoelectric element If the output of the subsequent transmission driver rises very slowly, the electrodes may not be charged to the desired final value, and thus, as shown in waveform 3606, a low output signal may occur. Here, the final amplitude is smaller than 3602. On the other hand, when the output signal of the transmission driver settles very quickly, the output signal of the transmission driver has a bandwidth larger than the bandwidth limit of the piezoelectric element, and thus, the extra energy can be dissipated as heat. Thus, in the embodiment, as shown in waveform 3608, the piezoelectric element can be charged at a speed such that it is fully charged but not too quickly. In the embodiment, the waveform 3608 representing the voltage potential between the upper electrode and the lower electrode as a function of time is closer in shape to the output of the transducer and has a smaller difference in shape, so the input signal bandwidth and the output signal bandwidth match better, and the energy loss due to heat is reduced. In the embodiment, the driving impedance of the transmission driver is optimized to reduce energy loss. In other words, the impedance of the transmission driver is designed to optimally drive the piezoelectric element with respect to the time constant required for heat dissipation and sufficient voltage regulation within the target time.

[0190] In an embodiment, the imager 120 may use harmonic imaging technology, where harmonic imaging refers to transmitting a pressure wave at the fundamental frequency of the membrane and receiving the reflected pressure wave at the second or higher harmonic frequency of the membrane. Generally, an image based on the reflected wave at the second or higher harmonic frequency has higher quality than an image based on the reflected wave at the fundamental frequency. The symmetry of the transmitted waveform can suppress the second or higher harmonic components of the transmitted wave, thus reducing the interference of these components with the second or higher harmonics in the reflected wave and enhancing the image quality of the harmonic imaging technology. In an embodiment, to reduce the second or higher harmonics in the transmitted wave, the waveform 3300 may have a 50% duty cycle.

[0191] In FIGS. 20 to 29, the array may include a plurality of line units, and each line unit may include a plurality of piezoelectric elements electrically coupled to each other. In an embodiment, the line unit may be driven by a plurality of pulses having a phase difference (or equivalently, a delay). By adjusting the phase, the resulting pressure wave can be steered at an angle. This is referred to as beamforming.

[0192] FIG. 37A shows a plot of the amplitude of the transmitted pressure wave as a function of the spatial position along the azimuthal axis of the transducer, according to an embodiment of the present disclosure. When the piezoelectric elements in the array are arranged two-dimensionally, the piezoelectric elements on the columns in the Y direction are connected to each other, and there are a number of columns along the X direction, the X direction is known as the azimuth direction, and the Y direction is known as the elevation direction. As shown in FIG. 37A, the transmitted pressure wave includes a main lobe and a plurality of side lobes. The main lobe can be used to scan the tissue target and has a high pressure amplitude. The side lobes have lower amplitudes but degrade the image quality. Therefore, it is desirable to reduce their amplitudes.

[0193] Figure 37B shows various types of windows for an apodization process according to an embodiment of the present disclosure. In Figure 37B, the x-axis represents the position of the piezoelectric element relative to the piezoelectric element at the center of the active window, and the y-axis represents the amplitude (or the weight applied to the piezoelectric element). As shown, for the rectangular window 3720, no weighting is given to any of the transmission lines, i.e., they all have a uniform amplitude (i.e., symbolically 1). On the other hand, when a weighting function such as that shown by the Hamming window 3722 is implemented, the central lines receive a greater weighting than the end lines. For example, to apply the Hamming window 3722 to the transducer tile 210 of Figure 3B, the piezoelectric elements in the leftmost column (denoted as -N in Figure 37B) and the piezoelectric elements in the rightmost column (denoted as N in Figure 37B) may have the lowest weights, while the piezoelectric elements in the central column may have the highest weights. This process is known as apodization. In an embodiment, the Hamming window 3722 shown is merely intended to be an example, and weightings of various types of windows may be applied. In an embodiment, apodization may be implemented by using a digital-to-analog converter (DAC), or by scaling the transmission driver output drive levels differently for different lines, such as by reducing the number of pixels on the line while maintaining the same drive level. The net effect is that the side lobe level can be reduced by the use of apodization, where the weighting of the transmission drive changes based on where a particular line is located within the activated transmission aperture. represents the position of the piezoelectric element relative to the piezoelectric element at the center of the active window, and the y-axis represents the amplitude (or the weight applied to the piezoelectric element) As shown, for the rectangular window 3720, no weighting is given to any of the transmission lines, i.e., they all have a uniform amplitude (i.e., symbolically 1). are. On the other hand, when a weighting function such as that shown by the Hamming window 3722 is implemented, the central lines receive a greater weighting than the end lines. For example, to apply the Hamming window 3722 to the transducer tile 210 of Figure 3B, the piezoelectric elements in the leftmost column (denoted as -N in Figure 37B) and the piezoelectric elements in the rightmost column (denoted as N in Figure 37B) may have the lowest weights, while the piezoelectric elements in the central column may have the highest weights. This process is known as apodization. In an embodiment, the Hamming window 3722 shown is merely intended to be an example, and weightings of various types of windows may be applied. In an embodiment, apodization may be implemented by using a digital-to-analog converter (DAC), or by scaling the transmission driver output drive levels differently for different lines, such as by reducing the number of pixels on the line while maintaining the same drive level. The net effect is that the side lobe level can be reduced by the use of apodization, where the weighting of the transmission drive changes based on where a particular line is located within the activated transmission aperture.

[0194] In an embodiment, a decrease in the voltage of a pulse or waveform can lower the temperature of the transducer surface. Alternatively, for a given maximum allowable transducer surface temperature, a transducer operating at a lower voltage may provide better probe performance and may result in a better quality image. For example, for a probe having 192 piezoelectric elements in order to reduce power consumption, a transmit pressure wave may be generated using only a portion of the probe (i.e., a subset of the piezoelectric elements), and the remaining elements may be scanned sequentially in time using a multiplexer. Thus, in a conventional system, only a portion of the transducer elements may be used at any given time to limit the temperature rise. In contrast, in an embodiment, a lower voltage probe enables more piezoelectric elements to be addressed simultaneously, thereby increasing the frame rate of the image and enhancing the image quality. Considerable power is also consumed in the receive path where the received signal is amplified using an LNA. The imaging system typically uses a number of receive channels, each with an amplifier. In an embodiment, temperature data can be used to turn off some of the receive channels in order to conserve power and lower the temperature.

[0195] In an embodiment, apodization can be achieved by varying the number of piezoelectric elements within each line unit according to a window function. In an embodiment, such window approximation may be achieved by electronically controlling the number of piezoelectric elements on a line or by wiring the transducer array with the required number of elements.

[0196] Generally, the heat generated by the probe can be a function of the pulse duration of the transmit pulse / waveform. Generally, to penetrate the pressure wave deeper within the target with a better signal-to-noise ratio (SNR) In some cases, piezoelectric elements may require long pulse trains. However, this also reduces the axial resolution and generates more heat in the piezoelectric element. Thus, in conventional systems, the number of pulses emitted is small, sometimes one or two. Longer pulses can generate more thermal energy, so their use in conventional systems is impractical. In contrast, in embodiments, pulses and waveforms 3300 and 3400 can have fairly low peak values, which can enable the use of long pulse trains, chirps, or other coded signaling. In embodiments, longer pulse trains do not reduce the axial resolution. This is because matched filtering is performed in the receiver to compress the waveform and recover the resolution. This technique allows for a better signal-to-noise ratio, enables the signal to penetrate deeper into the body, and permits high-quality imaging of deeper targets within the body.

[0197] In embodiments, a layer of polydimethylsiloxane (PDMS) or other impedance matching material may be spun onto the transducer elements of FIGS. 4-19. This layer improves the impedance match between the transducer element and the human body, thereby reducing the reflection or loss of pressure waves at the interface between the transducer element and the human body.

[0198] In FIGS. 20-29, a plurality of line units may be generated by connecting pixels in the y-direction (or x-direction), where one line unit (or an equivalent, a line element) refers to a plurality of piezoelectric elements that are electrically connected to each other. In embodiments, one or more line units can also be generated by connecting piezoelectric elements along the x-direction. continuing. In embodiments, the piezoelectric elements within a line unit may be fixedly wired.

[0199] As discussed in connection with FIG. 18A, each piezoelectric element 1806 may be electrically coupled to a circuit 1842, i.e., the number of piezoelectric elements within the transceiver substrate 1802 is the same as the number of circuits 1842 within the ASIC chip 1804. In such a case, the electrical connection of the piezoelectric elements within each column (or row) may be made electronically, i.e., fixed wiring conductors (e.g., 2007) for connecting the electrodes within the column (or row) are replaced by electronic switches. Stated another way, the piezoelectric elements within the line imager / unit may be electronically connected to each other. In the case of an electronically controlled line imager, the line imager / unit may be constructed by connecting each piezoelectric element of a two-dimensional matrix array to a corresponding control circuit (e.g., 1842) of a two-dimensional array of control circuits, where the control circuits are positioned spatially proximate to the pixels. To create a line element, a number of drivers controlling a column (or row) of pixels may be electronically turned on. In an embodiment, the number of drivers within each line imager / unit can be electrically modified under program control and is electronically adjustable, i.e., the line imager having piezoelectric elements is electrically configurable.

[0200] In an embodiment, the smaller capacitance of each pixel can be efficiently driven by a distributed drive circuit without other equalizing elements between the driver and the pixel, eliminating the difficulty of driving a very large line capacitance. In an embodiment, driver optimization allows for symmetry at the rise and fall edges, allows for better linearity at the transmit output, and enables harmonic imaging. (Symmetry was described in connection with FIGS. 33 and 34.) In an embodiment, electronic control may allow for programmable aperture size, transmit apodization, and horizontal or vertical steering control, all of which can improve image quality. In an embodiment, the line imager / unit configurable under electronic control may be electrically modified under program control. For example, in the y direction, if a smaller number of connected elements is desired, the number may be It may be adjusted by software control, and there is no need to re-spin the control electronic circuit or the piezoelectric array.

[0201] In an embodiment, each line unit may be composed of several sub-units and may be designed such that there is separate control for each sub-unit. The advantage of these sub-units is that it can reduce the difficulty of driving a large capacitive load for the line unit using a single external transmission driver. For example, when two line units are created instead of one line unit including all the piezoelectric elements in a column, two different transmission drivers (for example, 2816) may be used, and each transmission driver can control half of the load of the full line unit. Also, even when one driver is used, by driving the first half and the second half of the line unit separately, the driving state can be improved for lower resistance connections to both ends of the line unit.

[0202] In an embodiment, both the length and the orientation of the line unit may be controlled. For example, in FIGS. 20-29, the line unit may be arranged in both the x and y directions. As an example, in FIG. 30, the O electrodes (for example, 2003-11~ 2003-n1) along a column may be electrically coupled to form one line unit, and the O electrodes of other columns may be electrically coupled to form n line units extending along the x direction. More specifically, the line units extending along the x direction include n O electrodes (2003-12~2003-1n),…,(2003-n2~2003-nn). In an embodiment, the arrangement of the line units along the orthogonal directions may be possible by controlling the electrical circuit within the ASIC chip.

[0203] In FIGS. 20 - 30, each piezoelectric element may include two or more upper (X and T) electrodes. In an embodiment, the piezoelectric layer underlying these upper electrodes may be poled in the same or opposite directions. Multiple poling directions, when combined with an appropriate applied signal electric field, can result in an improvement in the transmission and reception sensitivity of the transducer and can also result in additional resonances that allow for a wider bandwidth.

[0204] In FIGS. 20 - 30, each array may have one or more membranes disposed under the piezoelectric elements. In an embodiment, the membranes may have multiple vibration modes. In an embodiment, one membrane may vibrate in a fundamental mode at a certain frequency, and another membrane may vibrate at a different frequency determined by the membrane design and the relative placement of the electrodes along with a different poling direction. In an embodiment, multiple membranes may be driven by the same set of electrodes and each membrane may have a different fundamental frequency. In an embodiment, each membrane may respond to a wide range of frequencies, increasing its bandwidth. Also, such transducers having different poling directions can enable high - bandwidth transducers and can help increase the transmission and reception sensitivity.

[0205] In FIGS. 22, 24, and 25, the X (or T) electrodes within a column may be electrically coupled to a conductor. In an embodiment, these conductors may be electrically coupled to a single common conductor. For example, in FIG. 22, conductors 2008 - 1 to 2208 - n may be electrically coupled to a single common conductor line, whereby all of the T electrodes within array 2200 can be grounded or connected to a common DC bias voltage.

[0206] In FIGS. 20 - 29, each array may include piezoelectric elements arranged in a two - dimensional array, and the number of elements in the x - direction may be the same as the number of elements in the y - direction. However, it should be apparent to those skilled in the art that the number of elements in the x - direction may be different from the number of elements in the y - direction.

[0207] In an embodiment, the ASIC chip (such as 1804) coupled to the transducer substrate (such as 1802) may include a temperature sensor that measures the surface temperature of the imaging device 120 facing the human body during operation. In an embodiment, the maximum allowable temperature may be adjusted, and this adjustment may limit the functionality of the imaging device because the temperature should not rise above an acceptable upper limit. In an embodiment, this temperature information may be used to improve the image quality. For example, when the temperature is below the maximum allowable limit, additional power may be consumed in the amplifier to reduce noise and improve the system signal-to-noise ratio for an improved quality image.

[0208] In an embodiment, the power consumed by the imaging device 120 increases as the number of simultaneously driven line units increases. All line units within the imaging device 120 may need to be driven to complete the transmission of the pressure wave from the entire aperture. If only a few line units are driven at a time to transmit a pressure wave, wait, and receive the reflected echo, it takes more time to complete one cycle of driving all the line units across the entire aperture, and the rate at which images are captured per second (frame rate) decreases. To improve this rate, more line units need to be driven at a time. In an embodiment, the temperature information may allow the imaging device 120 to drive more lines to improve the frame rate.

[0209] In FIGS. 20 to 30, each piezoelectric element may have one lower electrode (O) and one or more upper electrodes (X and T), and may have two or more resonant frequencies. For example, each piezoelectric element 2502 in FIG. 25 may have one lower electrode (O) and two upper electrodes, and the first upper electrode and the lower electrode (O) may respond to the first frequency f1, and the second upper electrode and the lower electrode (O) may respond to a second frequency f2 that may be different from f1. It may be.

[0210] In an embodiment, the charge generated during the reception mode is transferred to amplifiers such as 1811, 2810, 2814, 2910, 2914, 3010, 3016, 3128, and 3228. The amplified signal can then be further processed by various electrical components. Thus, it should be apparent to those skilled in the art that each of the amplifiers 1811, 2810, 2814, 2910, 2914, 3010, 3016, 3128, and 3228 refers to one or more electrical components / circuits for processing the charge signal, that is, each amplifier symbolically represents one or more electrical components / circuits for processing the charge signal.

[0211] FIG. 38 shows a schematic diagram of an imaging assembly 3800 according to an embodiment of the present disclosure. As shown, the imaging assembly 3800 may include a transceiver substrate 3801 having a piezoelectric element (not shown in FIG. 38); an ASIC chip 3802 electrically coupled to the transceiver substrate 3801; a receiver multiplexer 3820 electrically coupled to the ASIC chip 3802; a receiver analog front end (AFE) 3830; a transmitter multiplexer 3824 electrically coupled to the ASIC chip 3802; and a transmission beamformer 3834 electrically coupled to the second multiplexer 3824. In an embodiment, the ASIC chip 3802 may include a plurality of circuits 3804 configured to be connected to and drive a plurality of piezoelectric elements within the transceiver substrate 3801. In an embodiment, each circuit 3804 may include a receiver amplifier (or simply an amplifier) 3806 such as an LNA, a transmission driver 3808 for transmitting a signal to the piezoelectric element, and a switch 3810 that toggles between the amplifier 3806 and the transmission driver 3808. Those amplifiers may have a programmable gain and means for connecting them to the piezoelectric elements that need to be sensed. The transmission driver has means for optimizing their impedance and means for being connected to the piezoelectric element to be driven. It may also include a transmitter multiplexer 3824; and a transmission beamformer 3834 electrically coupled to the second multiplexer 3824. In an embodiment, the ASIC chip 3802 may include a plurality of circuits 3804 configured to be connected to and drive a plurality of piezoelectric elements within the transceiver substrate 3801. In an embodiment, each circuit 3804 may include a receiver amplifier (or simply an amplifier) 3806 such as an LNA, a transmission driver 3808 for transmitting a signal to the piezoelectric element, and a switch 3810 that toggles between the amplifier 3806 and the transmission driver 3808. Those amplifiers may have a programmable gain and means for connecting them to the piezoelectric elements that need to be sensed. The transmission driver has means for optimizing their impedance and means for being connected to the piezoelectric element to be driven. It may also include a switch 3810 that toggles between the amplifier 3806 and the transmission driver 3808. Those amplifiers may have a programmable gain and means for connecting them to the piezoelectric elements that need to be sensed. The transmission driver has means for optimizing their impedance and means for being connected to the piezoelectric element to be driven.

[0212] In an embodiment, the receiver multiplexer 3820 may include a plurality of switches 3822, and the receiver AFE 3830 may include a plurality of amplifiers 3832. In an embodiment, each of the switches 3822 can electrically connect / disconnect the circuit 3804 to / from the amplifier 3832. In an embodiment, the transmitter multiplexer 3824 may include a plurality of switches 3826, and the transmit beamformer 3834 may include a plurality of transmit drivers 3836, other circuits (not shown) for controlling the relative delay between the transmit driver waveforms of the various drivers, and other circuits (not shown) for controlling the frequency and number of pulses for each transmit driver. In an embodiment, each of the switches 3826 is turned on during a transmit operation and is connected to the circuit 3804, while the switch 3822 is turned off and the switch 3810 is connected to the transmit driver 3808. Similarly, during a receive operation, the switch 3826 is turned off while the switch 3822 is on, and the switch 3810 is connected to the amplifier 3806.

[0213] In an embodiment, the switch 3810 may be toggled to the transmit driver 3808 during a transmit mode and to the amplifier 3806 during a receive mode. In an embodiment, some of the switches 3822 may be closed so that the corresponding circuit 3804 can be set to a receive mode. Similarly, some of the switches 3826 may be closed so that the corresponding circuit 3804 can be set to a transmit mode. Since some of the switches 3822 and some of the switches 3826 can be closed simultaneously, the imager assembly can be operated simultaneously in both a transmit mode and a receive mode. Also, the receiver multiplexer 3820 and the transmitter multiplexer 3824 reduce the number of ASIC pins. In an embodiment, the receiver multiplexer 3820, the receiver AFE 3830, the transmitter multiplexer 3824 and the transmitter beamformer 3834 may be included in the circuit 215 of FIG. 2.

[0214] In an embodiment, each piezoelectric body may have more than two electrodes. One electrode may be in a transmission mode to generate a pressure wave, and at the same time, the other electrode may be in a reception mode to generate charges. This simultaneous operation of the transmission and reception modes may allow for three-dimensional imaging.

[0215] Although the present invention is capable of various modifications and alternative forms, specific examples thereof have been shown in the drawings and described in detail herein. However, it should be understood that the present invention is not limited to the particular forms disclosed, but on the contrary, the present invention covers any modifications, equivalents, and alternatives falling within the scope of the appended claims.

Claims

1. A transducer comprising: A two-dimensional array of piezoelectric elements, each piezoelectric element comprising at least one sub-piezoelectric element: A piezoelectric layer; A lower electrode disposed below the piezoelectric layer; and A two-dimensional array of piezoelectric elements having a first upper electrode disposed above the piezoelectric layer; and A first conductor, wherein a part of the first upper electrodes of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the first conductor. The transducer.

2. The transducer according to claim 1, wherein the piezoelectric element has a plurality of vibration modes exhibiting a wide frequency response.

3. The transducer according to claim 2, wherein each lower electrode of the piezoelectric elements in a column of the two-dimensional array is connected to a conductor, and those conductors are further connected together in the first column.

4. The transducer according to claim 3, wherein the piezoelectric elements are arranged in a plurality of columns, the lower electrodes of all the piezoelectric elements in a column are connected to a conductor, the conductors connected to the lower electrodes for different columns are separate, and the upper electrodes of all the piezoelectric elements in all columns are connected together.

5. Each piezoelectric element includes first and second sub-piezoelectric elements, each of the first and second sub-piezoelectric elements includes an upper electrode and a lower electrode, the lower electrode of the first sub-piezoelectric element is electrically coupled to the lower electrode of the second sub-piezoelectric element, a conductor connects the upper electrodes of all the first sub-piezoelectric elements in a column, another conductor connects all the upper electrodes of the second sub-piezoelectric elements in the same column, and the conductor connecting the lower electrodes is connected to all the piezoelectric elements in the array. The transducer according to claim 1.

6. The transducer according to claim 1, wherein each piezoelectric element includes first and second sub-piezoelectric elements, each of the first and second sub-piezoelectric elements includes an upper electrode and a lower electrode, the lower electrode of the first sub-piezoelectric element is electrically coupled to the lower electrode of the second sub-piezoelectric element, and the upper electrode of the first sub-piezoelectric element is electrically coupled to the upper electrode of the second sub-piezoelectric element.

7. The transducer according to claim 6, wherein each of the first and second sub-piezoelectric elements further includes an additional upper electrode, and the additional upper electrode of the first sub-piezoelectric element is electrically coupled to the additional upper electrode of the second sub-piezoelectric element.

8. It further has a second conductor, and the first upper electrode of the portion of the piezoelectric element in the second column of the two-dimensional array is electrically coupled to the second conductor, The first conductor is electrically coupled to the second conductor. The transducer according to claim 1.

9. Each piezoelectric element of the two-dimensional array further has a second upper electrode disposed on the upper surface of the piezoelectric layer, and the transducer is: It further has a second conductor, and the second upper electrode of the set of piezoelectric elements in the first column of the two-dimensional array is electrically coupled to the second conductor. The transducer according to claim 1.

10. The transducer according to claim 9, wherein each of the first and second upper electrodes has an annular shape, and the second upper electrode surrounds the first upper electrode.

11. It further has a third conductor, and the second upper electrode of the portion of the piezoelectric element in the second column of the two-dimensional array is electrically coupled to the third conductor, The third conductor is electrically coupled to the second conductor of the first column, and the first conductors of the first column and the second column are also electrically coupled. The transducer according to claim 9.

12. The transducer according to claim 9, wherein the first portion of the piezoelectric layer under the first upper electrode is poled in a first direction, and the second portion of the piezoelectric layer under the second upper electrode is poled in a second direction opposite to the first direction.

13. Each piezoelectric element of the two-dimensional array of piezoelectric elements further has a second upper electrode disposed on the upper surface of the piezoelectric layer, and the first and second upper electrodes of the portion of the piezoelectric element in the column of the two-dimensional array are electrically coupled to the first conductor, and the lower electrode is connected to a separate conductor for each piezoelectric element in the array. The transducer according to claim 1.

14. The first sub-piezoelectric element composed of the first upper electrode and the lower electrode has different frequency characteristics compared to the sub-piezoelectric element composed of the second upper electrode and the lower electrode, and allows a wider bandwidth for the composite element. The transducer according to claim 13.

15. The transducer according to claim 14, wherein all piezoelectric elements within a column are connected together with a common conductor for that column, and all upper electrodes of all piezoelectric elements are connected together using the common conductor and connected to a DC voltage.

16. The transducer according to claim 14, wherein the lower electrodes of all piezoelectric elements within the column are connected to a conductor that is further connected to a transmission driver during a transmission operation, and the lower electrodes are connected to a reception amplifier in a reception operation mode.

17. The transducer according to claim 15, wherein the lower electrode is connected to a transmission driver during a transmission operation and to a reception amplifier during a reception operation.

18. Each piezoelectric element of the two-dimensional array of piezoelectric elements further has second, third, and fourth upper electrodes disposed on the upper surface of the piezoelectric layer, and the second upper electrode of the set of piezoelectric elements in the first column of the two-dimensional array is electrically coupled to the first conductor, and the transducer further comprises: a second conductor, wherein the third and fourth upper electrodes of a portion of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the second conductor, The transducer according to claim 1.

19. a third conductor, wherein the first and second upper electrodes of a portion of the piezoelectric elements in the second column of the two-dimensional array are electrically coupled to the third conductor; a fourth conductor, wherein the third and fourth upper electrodes of a portion of the piezoelectric elements in the second column of the two-dimensional array are electrically coupled to the fourth conductor, and the transducer further comprises: the first conductor is electrically coupled to the third conductor, and the second conductor is electrically coupled to the fourth conductor. The transducer according to claim 18.

20. Each piezoelectric element includes first and second sub-piezoelectric elements, each of the first and second sub-piezoelectric elements includes an upper electrode and a lower electrode, the lower electrode of the first sub-piezoelectric element is electrically coupled to the lower electrode of the second sub-piezoelectric element, a conductor connects all upper electrodes of all first piezoelectric elements within a column, another conductor connects all upper electrodes of all second sub-piezoelectric elements within a row, and the conductor connecting the lower electrodes is connected to all piezoelectric elements within the array. The transducer according to claim 1.

21. The transducer according to claim 5, wherein each column consisting of the first sub-piezoelectric elements is connected to a receiver, and another column consisting of the second sub-piezoelectric elements is alternately operated in a transmission mode or a reception mode.

22. The transducer according to claim 20, wherein each row consisting of the first sub-piezoelectric elements is connected to a receiver, and another column consisting of the second sub-piezoelectric elements is alternately operated in a transmission mode or a reception mode.

23. Further comprising an application-specific integrated circuit (ASIC) chip having an array of transmission driver circuits, each transmission driver circuit being electrically coupled to a lower electrode of a corresponding piezoelectric element of the two-dimensional array of piezoelectric elements, wherein the number of transmission driver circuits in the application-specific integrated circuit (ASIC) chip is the same as the number of the piezoelectric elements in the two-dimensional array of piezoelectric elements. The transducer according to claim 1.

24. Further comprising a substrate on which the two-dimensional array of piezoelectric elements is disposed, wherein the first conductor is a metal conductor layer deposited on at least one of the substrate and the application-specific integrated circuit (ASIC) chip. The transducer according to claim 23.

25. Further comprising a layer disposed on the application-specific integrated circuit (ASIC) chip configured to absorb a part of the pressure wave transmitted by the piezoelectric element. The transducer according to claim 23.

26. The transducer according to claim 23, wherein each transmission driver circuit is configured to transmit at least one of a unipolar signal, a multi-level signal, and a chirp signal.

27. The transducer according to claim 23, wherein the application-specific integrated circuit (ASIC) chip performs at least one of transmitting a signal to the piezoelectric element, receiving a signal from the piezoelectric element, amplifying a signal received from the piezoelectric element, polling the piezoelectric element, and communicating with an external electronic system.

28. The transducer according to claim 23, wherein the application-specific integrated circuit (ASIC) chip is integrated with the two-dimensional array of piezoelectric elements by one or more interconnect bumps.

29. The transducer according to claim 23, wherein the application-specific integrated circuit (ASIC) chip includes a low-noise amplifier (LNA) operating in a charge sensing mode.

30. The transducer according to claim 29, wherein the low-noise amplifier (LNA) has a programmable gain. **Claim 31** The transducer according to claim 30, wherein the gain is configurable in real time to provide time gain compensation. **Claim 32** The transducer according to claim 23, wherein the application-specific integrated circuit (ASIC) chip utilizes a serial peripheral interface (SPI) mode for communication. **Claim 33** The transducer according to claim 31, wherein the application-specific integrated circuit (ASIC) chip includes at least one transmit signal line and at least one receive signal line, and the at least one transmit signal line and the at least one receive signal line are multiplexed on a single wire for communication with an external electronic device. **Claim 34** The transducer according to claim 31, further comprising at least one temperature sensor for measuring the temperature of the imaging device. **Claim 35** The transducer according to claim 25, wherein the application-specific integrated circuit (ASIC) chip includes a low-noise amplifier (LNA), receives temperature data from the at least one temperature sensor, and uses the temperature data to adjust the transmit and receive operations to lower the temperature. **Claim 36** The transducer according to claim 32, wherein the number of columns transmitted in one frame is reduced. **Claim 37** The transducer according to claim 35, wherein the number of receive channels, each comprising a low-noise amplifier (LNA) and other receive circuitry per channel, is reduced by powering off to lower the temperature. **Claim 38** The transducer according to claim 26, wherein the frame rate is reduced to lower the temperature. **Claim 39** The transducer according to claim 23, wherein one of the transmit driver circuits is unipolar. **Claim 40** The transducer according to claim 23, wherein one of the transmit driver circuits is configured to generate a signal having equal on and off times and symmetric rise and fall times. **Claim 41** The transducer according to claim 23, wherein one of the transmit drivers is programmable and designed to maximize the acoustic power from the transducer without excessive heating. **Claim 42** The transducer according to claim 1, wherein the shape of one of the piezoelectric elements is different from the shape of another piezoelectric element among the piezoelectric elements.

43. The transducer according to claim 1, wherein the size of one of the piezoelectric elements is different from the size of another piezoelectric element among the piezoelectric elements.

44. The transducer according to claim 1, wherein each of the piezoelectric elements is a piezoelectric micromachined ultrasonic transducer (pMUT) that vibrates in a lateral mode.

45. It is disposed on the piezoelectric array facing the object to be imaged, and further has a layer configured to reduce the impedance mismatch between the piezoelectric element and the object to be imaged and the object. The transducer according to claim 1.

46. The transducer according to claim 45, wherein the layer is made of a room temperature vulcanizing (RTV) material.

47. The transducer according to claim 45, wherein the thickness of the layer is one quarter of the wavelength of the pressure wave generated by the piezoelectric element.

48. The transducer according to claim 1, wherein the first conductor is electrically coupled to a DC bias voltage during operation.

49. The transducer according to claim 1, wherein the lower electrode is a signal conductor and is connected to one of a transmission circuit and a reception circuit, and the upper electrode is connected to a DC bias source including ground.

50. The transducer according to claim 29, wherein each of the transmission circuit and the reception circuit is an integrated circuit.

51. An imaging device comprising: A two-dimensional array of piezoelectric elements, each piezoelectric element of the two-dimensional array of piezoelectric elements includes at least one sub-piezoelectric element, A piezoelectric layer; A lower electrode disposed below the piezoelectric layer; and A two-dimensional array having first and second upper electrodes disposed above the piezoelectric layer; A first conductor, wherein a part of the first upper electrodes of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the first conductor; A first electrical circuit electrically coupled to the first conductor and configured to process a signal received through the first conductor; A second conductor, wherein a part of the second upper electrodes of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the second conductor; A switch having a first end and a second end, wherein the first end is electrically coupled to the second conductor; A second electrical circuit for processing signals; And a transmission driver for sending signals to the second conductor, wherein the second end of the switch is selectively coupled to one of the second electrical circuit and the transmission driver. An imaging device.

52. The imaging device according to claim 51, wherein the first and second electrical circuits include low-noise amplifiers.

53. An imaging device comprising: A two-dimensional array of piezoelectric elements, each piezoelectric element of the two-dimensional array of piezoelectric elements including at least one sub-piezoelectric element, a piezoelectric layer; a lower electrode disposed below the piezoelectric layer; and first and second upper electrodes disposed above the piezoelectric layer. A two-dimensional array; A first conductor, wherein a part of the first upper electrodes of the piezoelectric elements in the first row of the two-dimensional array are electrically coupled to the first conductor; A first electrical circuit electrically coupled to the first conductor and configured to process signals received through the first conductor; A second conductor, wherein a part of the second upper electrodes of the piezoelectric elements in the first column of the two-dimensional array are electrically coupled to the second conductor; A switch having a first end and a second end, wherein the first end is electrically coupled to the second conductor; A second electrical circuit for processing signals; And a transmission driver for sending signals to the second conductor, wherein the second end of the switch is selectively coupled to one of the second electrical circuit and the transmission driver. An imaging device.

54. The imaging device according to claim 53, wherein the first and second electrical circuits include low-noise amplifiers.

55. An imaging device having a first substrate and a second substrate, Wherein the first substrate: Has a two-dimensional array of piezoelectric elements, and each piezoelectric element of the two-dimensional array of piezoelectric elements: A piezoelectric layer; A lower electrode disposed below the piezoelectric layer; First and second upper electrodes disposed above the piezoelectric layer; And first and second conductors electrically coupled to the first and second upper electrodes, respectively; Wherein the second substrate: Has a two-dimensional array of circuit elements, and each circuit element of the two-dimensional array of circuit elements: A first electrical circuit electrically coupled to the first conductor of the piezoelectric element and configured to process a signal received through the first conductor; A switch having a first end and a second end, the first end being electrically coupled to the second conductor of the piezoelectric element; A second electrical circuit for processing signals; And a transmission driver for sending a signal to the second conductor, the second end of the switch being selectively coupled to one of the second electrical circuit and the transmission driver; An imaging device. **Claim 56** A circuit for controlling a plurality of piezoelectric elements: A first conductor for transmitting a drive signal to one or more of the plurality of piezoelectric elements; And a second conductor for transmitting a sensor signal from one or more of the plurality of piezoelectric elements, Each circuit element of the plurality of circuit elements: A first switch having a first end electrically coupled to the second conductor and a first electrode of the piezoelectric element; A second switch having a first end and a second end, the first end of the second switch being electrically coupled to the first conductor; A transmission driver electrically coupled to the second end of the second switch and configured to transmit a signal to the first electrode of the piezoelectric element when receiving the drive signal through the second end of the second switch; A third switch having first and second ends, the first end of the third switch being electrically coupled to the second end of the second switch, and the second end of the third switch being electrically coupled to an electrode of the piezoelectric element; A circuit. **Claim 57** The circuit according to claim 56, wherein the second conductor is electrically coupled to a DC bias voltage during operation of the plurality of piezoelectric elements. **Claim 58** Further comprising a third conductor, Each circuit element of the plurality of circuit elements further having a fourth switch having a first end and a second end, the first end of the fourth switch being electrically coupled to the third conductor, and the second end of the fourth switch being electrically coupled to a third electrode of the piezoelectric element; The circuit according to claim 56. **Claim 59** The circuit according to claim 58, wherein the third conductor is electrically coupled to a DC bias voltage during operation of the plurality of piezoelectric elements. **Claim 60** further comprising an electrical circuit that is electrically coupled to the second conductor and configured to process signals received through the second conductor The circuit according to claim 56 **Claim 61** A method of poling a piezoelectric element electrically coupled to an application specific integrated circuit (ASIC) chip, the piezoelectric element including a lower electrode, a piezoelectric layer disposed on the lower electrode, and first and second upper electrodes disposed on the piezoelectric layer, the method comprising:[[]] electrically connecting the lower electrode to ground; applying a positive voltage to the first upper electrode; applying a negative voltage to the second upper electrode; exposing the piezoelectric element to a temperature over a long period of time, whereby a first portion of the piezoelectric layer under the first upper electrode is poled in a first direction and a second portion of the piezoelectric layer under the second upper electrode is poled in a second direction opposite to the first direction Method **Claim 62** An imaging device comprising:[[]] a two-dimensional array of piezoelectric elements, each piezoelectric element including at least one sub-piezoelectric element,[[]] a piezoelectric layer; a lower electrode disposed under the piezoelectric layer; and a two-dimensional array having a first upper electrode disposed above the piezoelectric layer; and an application specific integrated circuit (ASIC) chip having an array of circuits for driving the two-dimensional array of piezoelectric elements, each of the circuits being electrically coupled to a corresponding piezoelectric element,[[]] a first row or line of the imaging device including a portion of the piezoelectric elements in a first column of the two-dimensional array being formed by simultaneously turning on a portion of the circuits that control the portion of the piezoelectric elements in the first column of the two-dimensional array Imaging device **Claim 63** The imaging device according to claim 62, wherein the number of the transmission driver circuits in the application specific integrated circuit (ASIC) chip is less than or equal to the number of the piezoelectric elements in the two-dimensional array of piezoelectric elements **Claim 64** A second line including a portion of the piezoelectric elements in a second column of the two-dimensional array is formed by turning on a portion of the circuits that control the portion of the piezoelectric elements in the second column of the two-dimensional array, and the number of the piezoelectric elements in the first line is different from the number of the piezoelectric elements in the second line The imaging device according to claim 62 **Claim 65** The imaging device according to claim 62, wherein the first column or line of the imager is coupled to a transmission driver that applies an electrical signal to the first line so that the piezoelectric element in the first line emits a pressure wave.

66. The imaging device according to claim 62, wherein the first column or line of the imager is coupled to a receiving amplifier that receives an electrical signal from the first line and processes the electrical signal.

67. Each of the circuits includes a receiving amplifier, and further includes a multiplexer that is electrically coupled to the receiving amplifier of the circuit during the receiving mode and is configured to multiplex signals from the receiving amplifier. The imaging device according to claim 62.

68. The imaging device according to claim 67, further comprising a receiver analog front end (AFE) electrically coupled to the multiplexer. The imaging device according to claim 67.

69. Each of the circuits includes a transmission driver, and further includes a multiplexer that is coupled to the transmission driver of the circuit during the transmission mode and is configured to multiplex signals to be sent to the transmission driver. The imaging device according to claim 62.

70. The imaging device according to claim 69, further comprising a transmission beamformer electrically coupled to the multiplexer. The imaging device according to claim 69.

71. The imaging device according to claim 69, wherein the impedance of the transmission driver is programmable and is designed to maximize the acoustic power from the transducer without excessive heating.

72. During a first period, all columns of the imager are driven by a transmission driver, the transmission driver consists of some circuits on one or more integrated circuits connected by switches under electronic control, each column of the imager is connected to a receiving amplifier, and the amplifier consists of some circuits connected by switches under program control. The imaging device according to claim 62.

73. The imaging device according to claim 62, wherein portions of the transmission driver are implemented in a field programmable gate array (FPGA)-based transmission beamformer.

74. The imaging device according to claim 62, wherein various parts of the receiving amplifier are implemented in an analog front end including a resulting digital output interfaced to a time gain amplifier, a low-pass filter, an analog-to-digital converter, a digital decimator, and a field programmable gate array (FPGA).

75. The transducer according to claim 1, wherein the piezoelectric element is configured to transmit and receive at least one ultrasonic waveform having a bandwidth including a plurality of frequencies of vibration of each piezoelectric element, and transmission of a pressure wave from the piezoelectric element is achieved by applying a voltage pulse for an appropriate time period between the upper electrode and the lower electrode.

76. The piezoelectric element has at least one configured to transmit and receive ultrasonic waveforms having a bandwidth including a plurality of frequencies of vibration of each piezoelectric element, and transmission of a pressure wave from the piezoelectric element is achieved by applying a voltage pulse for an appropriate time period between the upper electrode and the lower electrode. The transducer according to claim 2.

77. The transducer according to claim 76, wherein the transducer has only a transmission function.

78. The transducer according to claim 76, wherein the maximum positive amplitude of the AC drive voltage is +5 V, the maximum negative voltage is -5 V, and both voltages are nominal values with a tolerance within 5%.

79. The transducer according to claim 76, comprising additional columns, wherein the amplitude of the transmission driver varies for the additional columns.

Images