PZT coated membrane structures for micromachined ultrasonic transducers

Micromachined ultrasonic transducers (MUT) are investigated for phased arrays in high frequency acoustic imaging to overcome resolution and frequency limits of reticulated bulk PZT transducers applied today. In this paper, thin SiO/sub 2//Si membranes coated with (100)-textured Pb(Zr/sub x/Ti/sub 1-x/)O/sub 3/ (PZT) thin films deposited by sol-gel techniques are studied for pMUT applications. The first part of this work is devoted to fabrication processes. Major issues are the quality of the PZT films, the overall low stress of the membranes and the precision of the patterning processes. A second part deals with the characterization of cantilever and membrane structures. The findings are used to optimize a transducer design for medical imaging in the range of 5MHz.