Micromachined ultrasonic transducers and arrays based on piezoelectric thick film

This paper reports on the design, fabrication, and characterization of diaphragm-type piezoelectric micromachined ultrasonic transducer (pMUT) and arrays. A combination of piezoelectric composite thick film techniques and silicon micromachining has been proven to be a promising approach for a batch production of pMUTs, especially pMUT transmitter arrays for ultrasound radiation. In this paper, some important issues related to the pMUT element design and micromachining processes are addressed. Thanks to the well-developed processing technology, pMUTs and arrays operating at different resonance frequencies by dimension variation have been successfully fabricated with a high yield for possible mass manufacturing. The characterization of piezoelectric composite thick film will be briefly reported. The performance of the prototype devices has been characterized in terms of vibration modes, dependency of the resonance frequency on bias voltage, nonlinearity, electromechanical coupling efficiency, equivalent circuit, output sound pressure level and directivity of a two-dimensional pMUT array. PACS 85.50.-n; 85.85.+j