In vivo real-time 3-D intracardiac echo using PMUT arrays

Abstract

Piezoelectric micromachined ultrasound transducer (PMUT) matrix arrays were fabricated containing novel through-silicon interconnects and integrated into intracardiac catheters for in vivo real-time 3-D imaging. PMUT arrays with rectangular apertures containing 256 and 512 active elements were fabricated and operated at 5 MHz. The arrays were bulk micromachined in silicon-on-insulator substrates, and contained flexural unimorph membranes comprising the device silicon, lead zirconate titanate (PZT), and electrode layers. Through-silicon interconnects were fabricated by depositing a thin-film conformal copper layer in the bulk micromachined via under each PMUT membrane and photolithographically patterning this copper layer on the back of the substrate to facilitate contact with the individually addressable matrix array elements. Cable assemblies containing insulated 45-AWG copper wires and a termination silicon substrate were thermocompression bonded to the PMUT substrate for signal wire interconnection to the PMUT array. Side-viewing 14-Fr catheters were fabricated and introduced through the femoral vein in an adult porcine model. Real-time 3-D images were acquired from the right atrium using a prototype ultrasound scanner. Full 60° × 60° volume sectors were obtained with penetration depth of 8 to 10 cm at frame rates of 26 to 31 volumes per second.

Ultrasonic fingerprint sensor using a piezoelectric micromachined ultrasonic transducer array integrated with complementary metal oxide semiconductor electronics

“…Whereas a CMUT is based on capacitive electrodes separated by a submicron vacuum gap, a PMUT consists of a solid piezoelectric capacitor, greatly simplifying fabrication and improving mechanical robustness. While earlier PMUTs have been based on PZT 6 and ZnO, 7 the PMUTs demonstrated here are based on piezoelectric aluminum nitride (AlN), a material that is compatible with CMOS fabrication and used in low-cost, high-volume devices such as bulkacoustic wave filters. 8 The sensor's electronic architecture and performance are described in Ref.…”

“…A single AlGe bond at the bottom of each column of 8 PMUTs provides a contact to that column's top electrode layer, while individual annular AlGe bond rings provide a contact to the circular bottom electrode of each PMUT. While MUT-CMOS integration has been achieved using through-silicon vias and solder-ball flip-chip bonding, 6,11 here the bonding is conducted at wafer-scale and without the need for costly through-silicon vias, both dramatically reducing manufacturing costs and risks. The same manufacturing process has been used to realize PMUT arrays having cylindrical acoustic waveguides above the PMUT array.…”

Single-Element Omnidirectional Piezoelectric Ultrasound Transducer for under Water Communication

“…In both cases, the beam pattern of the transducer is directional. However, to cover the whole space, e.g., for 3D imaging or communication, we need very complex structures, such as mechanical rotary movement or a folded surface covered with an array of transducers, which are also limited to short distance application [3].…”

Direct Digital Demultiplexing of Analog TDM Signals for Cable Reduction in Ultrasound Imaging Catheters

“…Direct connection to each of the elements in the 2D arrays is either impossible or very limiting due to size of the catheter, especially in the case of small sized catheters for intracardiac echography (ICE) [2]. It is partially because of these limitations that current 3D ICE probes do not have a large field of view [3].…”