Capacitive micromachined ultrasonic transducers (CMUTs) have been subject to extensive research for the last two decades. Although they were initially developed for air-coupled applications, today their main application space is medical imaging and therapy. This paper first presents a brief description of CMUTs, their basic structure and operating principles. Our progression of developing several generations of fabrication processes is discussed with an emphasis on the advantages and disadvantages of each process. Monolithic and hybrid approaches for integrating CMUTs with supporting integrated circuits are surveyed. Several prototype transducer arrays with integrated front-end electronic circuits we developed and their use for 2D and 3D, anatomical and functional imaging, and ablative therapies are described. The presented results prove the CMUT as a micro-electro-mechanical systems technology for many medical diagnostic and therapeutic applications.

/pdf/capacitive-micromachined-ultrasonic-transducers-for-medical-1c8bymjvrh.pdf

Capacitive micromachined ultrasonic transducers for medical imaging and therapy

In real-time ultrasonic 3-D imaging, in addition to difficulties in fabricating and interconnecting 2-D transducer arrays with hundreds of elements, there are also challenges in acquiring and processing data from a large number of ultrasound channels. The coarray (spatial convolution of the transmit and receive arrays) can be used to find efficient array designs that capture all of the spatial frequency content (a transmit-receive element combination corresponds to a spatial frequency) with a reduced number of active channels and firing events. Eliminating the redundancies in the transmit-receive element combinations and firing events reduces the overall system complexity and improves the frame rate. Here we explore four reduced redundancy 2-D array configurations for miniature 3-D ultrasonic imaging systems. Our approach is based on 1) coarray design with reduced redundancy using different subsets of linear arrays constituting the 2-D transducer array, and 2) 3-D scanning using fan-beams (narrow in one dimension and broad in the other dimension) generated by the transmit linear arrays. We form the overall array response through coherent summation of the individual responses of each transmit-receive array pairs. We present theoretical and simulated point spread functions of the array configurations along with quantitative comparison in terms of the front-end complexity and image quality.

Minimally Redundant 2-D Array Designs for 3-D Medical Ultrasound Imaging

A system for acquiring an ultrasound signal comprises a signal processing unit adapted for acquiring a received ultrasound signal from an ultrasound transducer having a plurality of elements. The system is adapted to receive ultrasound signals having a frequency of at least 20 megahertz (MHz) with a transducer having a field of view of at least 5.0 millimeters (mm) at a frame rate of at least 20 frames per second (fps). The signal processing can further produce an ultrasound image from the acquired ultrasound signal. The transducer can be a linear array transducer, a phased array transducer, a two-dimensional (2-D) array transducer, or a curved array transducer.

High frequency array ultrasound system

A semiconductor device has a carrier with a die attach area. A semiconductor die is mounted to the die attach area with a back surface opposite the carrier. A modular interconnect unit is mounted over the carrier and around or in a peripheral region around the semiconductor die such that the modular interconnect unit is offset from the back surface of the semiconductor die. An encapsulant is deposited over the carrier, semiconductor die, and modular interconnect unit. A first portion of the encapsulant is removed to expose the semiconductor die and a second portion is removed to expose the modular interconnect unit. The carrier is removed. An interconnect structure is formed over the semiconductor die and modular interconnect unit. The modular interconnect unit includes a vertical interconnect structures or bumps through the semiconductor device. The modular interconnect unit forms part of an interlocking pattern around the semiconductor die.

Semiconductor device and method of forming a fan-out PoP device with PWB vertical interconnect units

Packaged microelectronic devices and methods for manufacturing packaged microelectronic devices are disclosed herein. In one embodiment, a packaged microelectronic device can include a support member, a first die attached to the support member, and a second die attached to the first die in a stacked configuration. The device can also include an attachment feature between the first and second dies. The attachment feature can be composed of a dielectric adhesive material. The attachment feature includes (a) a single, unitary structure covering at least approximately all of the back side of the second die, and (b) a plurality of interconnect structures electrically coupled to internal active features of both the first die and the second die.

Packaged microelectronic devices and methods for manufacturing packaged microelectronic devices

A modular and tileable sensor array with routing in the interposer carrying the signals from the sensors to the integrated circuits. In one embodiment a large area modular sensor array assembly includes one or more tileable modules coupled together. The tileable modules have a plurality of transducer cells forming a sensor, an interposer coupled on a first side to the plurality of transducer cells by a plurality, one or more integrated circuits coupled to a second side of the interposer, wherein the interposer is configured to form the connection of at least some of the transducer cells to the integrated circuits, and one or more input/output connectors coupled to the interposer and providing an external interface.

Large area modular sensor array assembly and method for making the same

An ultrasound probe includes a transducer comprising an array of transducer elements removably disposed in a head portion. At least one or more stages of electronic circuit units is removably coupled to the transducer and configured to excite the transducer. A handle portion is detachably coupled to the head portion. The head portion and the handle portion are disposed enclosing the at least one or more stages of electronic circuit units. The ultrasound probe is used for one dimensional applications, two dimensional applications, and volumetric applications.

Ultrasound probe with replaceable head portion

A system for improving the acoustic performance of an ultrasound transducer by reducing artifacts within the acoustic spectrum is disclosed. The system includes an acoustic layer having an array of acoustic elements, a dematching layer coupled to the acoustic layer and having an acoustic impedance greater than an acoustic impedance of the acoustic layer, and an interposer layer coupled to the dematching layer and comprising a substrate and a plurality of conductive element. The interposer layer is formed to have an acoustic impedance lower than the acoustic impedance of the dematching layer. The ultrasound transducer also includes an integrated circuit coupled to the interposer layer and electrically connected to the array of acoustic elements through the dematching layer and the interposer layer.

Ultrasound transducer with improved acoustic performance

A modular sensor assembly and methods of fabricating a modular sensor assembly are provided. The modular sensor assembly includes a sensor array coupled to an electronics array in a stacked configuration. The sensor array comprises a plurality of sensor modules, each comprising a plurality of sensor sub-arrays. The electronics array comprises a plurality of integrated circuit modules, each comprising a plurality of integrated circuit chips. The sensor modules may be coupled to the electronics modules via flip chip technology.

Modular sensor assembly and methods of fabricating the same

An ultrasonic monitoring system is formed with a probe unit. In one example an array of transducer cells is arranged in rows and columns formed along a first plane with a first pitch along a first direction. An integrated circuit including an array of circuit cells is formed along a second plane parallel to the first plane. The circuit cells are spaced apart along the first direction at a second pitch smaller than the first pitch. A first of the transducer cells is vertically aligned, along a direction normal to one of the planes, with a first of the circuit cells and having a connection thereto. A second of the transducer cells is offset from vertical alignment with respect to the position of a second circuit cell so as to not overlie the second circuit cell. A connection subsystem is positioned between the array of transducer cells and the array of circuit cells, configured to form connection of the first transducer cell to the first circuit cell and connection of the second transducer cell with the second circuit cell.

Charles Gerard Woychik

Papers

Large area modular sensor array assembly and method for making the same

Ultrasound probe with replaceable head portion

Ultrasound transducer with improved acoustic performance

Modular sensor assembly and methods of fabricating the same

Monitoring or imaging system with interconnect structure for large area sensor array