2F-5 Surface Preparation of 1-3 Piezocomposite Material for Microfabrication of High Frequency Transducer Arrays

A key issue in the development of ultrasound imaging arrays to operate at frequencies above 30 MHz is the need for photolithographic patterning of array electrodes. To achieve this directly on a 1-3 piezocomposite requires planar, parallel and smooth surfaces. This paper reports an investigation of the surface finishing of 1-3 piezocomposite material by mechanical lapping and/polishing that has demonstrated that excellent surface flatness can be obtained. Subsequently, high frequency array elements have been fabricated on these surfaces using a low temperature lift-off photolithography process. A 50 MHz linear array with 30 mum element pitch has been patterned on the lapped and polished surface of a low frequency 1-3 piezocomposite. Good electrode edge definition and electrical contact to the composite were obtained. Additionally, patterning has been demonstrated on a fine-scale composite, itself suitable for operation above 30 MHz.