Integrated silicon-PVF₂acoustic transducer arrays

Abstract

A new type of transducer array has been designed which employs a piezoelectric polymer, polyvinylidene fluoride (PVF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ), as the sensing material. Acoustic properties possessed by this piezoelectric polymer provide a reasonable match to those of the human body making it very attractive for medical ultrasonic imaging systems. Using planar integrated-circuit (IC) technology, an array of MOSFET input amplifiers is fabricated on a silicon wafer. A single sheet of PVF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> is bonded to the surface of the wafer. Spatially varying acoustic signals detected by the PVF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> are converted to corresponding charge distributions on the underlying array of amplifiers. A linear 34-element receiving transducer array has been built and evaulated. Array transverse dimensions are 14.7 × 9 mm, so that the silicon die area is approximately 1.32 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Individual transducers are 0.42 × 9 mm corresponding to the requirements of a particular system. Associated with each of the 34 transducers is a DMOS-bipolar cascode amplifier. Experimentally measured transducer impulse response decays 20 dB in two cycles. Using silicon technology, arrays of almost arbitrary size and complexity appear feasible.