Bjørn Angelsen

A new design for a high frequency broadband ultrasound transducer using micromachined Silicon

We present a new design for a small ultrasound transducer, using thick-film PZT on Silicon to obtain high frequency and large bandwidth. The transducer is intended for use in high resolution medical imaging systems, e.g. intravascular catheters. Air is used as backing material for the PZT film, and the ultrasound pulses are transmitted through the silicon substrate, The silicon substrate is micromachined to build three acoustic matching layers, to optimize the acoustic coupling between the active PZT layer and the tissue, and achieve a large bandwidth. We present the fabrication steps for manufacturing such a transducer, together with 1D analytical calculations and 3D FEM simulations of its performance. Our calculations show that the proposed design will have a 3 dB bandwidth ranging from 37 MHz to 102 MHz, or 94% bandwidth at center frequency 70 MHz. FEM model simulations of the structure support the analytical calculations, showing good agreement between analytical and simulation results.