cMUT echographic probes: design and fabrication process

The electrostatic capacitive, silicon micro fabricated, ultrasonic transducer (cMUT), approached in the last years, is a new promising alternative to the piezoelectric transducer for echographic probes. The cMUT transducer inherently has a larger bandwidth for immersion application and, because it takes advantage of the well established microelectronic technology it is, potentially, less expensive and gives much more flexibility in the design of complex 1D and 2D arrays than piezoelectric transducers. In perspective, a further advantage of the cMUT is the possibility to be integrated with the front-end electronics on the same silicon wafer. In this paper the design and the fabrication process of a 64-elements cMUT probe is described. We are fabricating an array with a pitch of 0.245 mm, kerf 27 Am, elevation 14 mm, glued on a commercial backing and soldered using a typical connection-comb to permit the electrical connection to the printing circuits, as used in commercial probes. With the addition of the biasing voltage, the probe is ready to be connected to a commercial echographic system, like Technos® (ESAOTE). Due to the inherently large bandwidth, the probe can be used as a linear array at about 7 MHz, and as a phased array at about MHZ..