Fabrication and characterisation of annular thickness mode piezoelectric micro ultrasonic transducers

Micromachining techniques, in combination with low temperature ceramic composite sol gel processing, have been used to fabricate annular array thickness-mode piezoelectric micro ultrasonic transducers (Tm-pMUT). The processing techniques of low temperature (720degC) composite sol gel ceramic (sol + ceramic powder) deposition and wet etching will be described and device architectures demonstrated. Using these techniques, high quality PZT materials with near bulk permittivity have been obtained. The Tm-pMUT device resonated in the range of 50-100 MHz with a kt of between 0.3 and 0.4 depending on processing conditions. Examples of devices will be presented along with results of electrical and resonance measurements.