Micromachined piezoelectric ultrasonic transducers based on parylene diaphragm in silicon substrate

This paper describes the fabrication and characterization of a micromachined ultrasonic airborne transducer built on a 1 μm thick parylene polymer diaphragm (flat 5000*5000 μm² square diaphragm) with electrodes and a piezoelectric ZnO film in a silicon substrate. The sound pressure level at 20 mm away from the fabricated transducer is measured to be around 0.44 Pa at 32.9 kHz (the transducer is driven by a 11 V_rms sinusoidal source and measured with B&K 4135 microphone). The vibration amplitude is measured (with a laser Doppler meter) to be about 1 μm at 32.9 kHz. Finite element analysis with ANSYS 5.6 has been performed to analyze the static and dynamic behaviors of the transducer under both pressure and voltage loadings