Design and fabrication of a lead zirconate titanate (PZT) thin film acoustic sensor

Piezoelectric MEMS acoustic sensors have potential applications in a wide variety of applications including hearing aids, surveillance, heart monitoring, etc. For each of these systems and many others, the acoustic sensors must be miniaturized and have low power requirements. A piezoelectric based microphone can provide a solution to these requirements, as they offer the ability to passively sense without the power requirements of condenser or piezoresistive microphone counterparts. This research effort reports on the design and fabrication of a piezoelectric PZT based acoustic sensor. A circular clamped membrane consisting of a dielectric for structural support and a piezoelectric actuator has been fabricated on a silicon wafer using silicon deep reactive ion etching (DRIE). Sensors ranging from 500-2000 microns in diameter have been fabricated and characterized using scanning laser Doppler vibrometry and calibrated acoustic tone sources. The PZT sensors exhibited a sensitivity of 97.9-920 nV/Pa depending on geometry.