Piezoelectric microresonant pressure sensor using aluminum nitride

Abstract

This paper presents the design and fabrication of a silicon island supported resonating beam-based micropressure sensor with piezoelectric excitation and detection. The sensor consists of a silicon frame with silicon islands supporting a silicon nitride (SIN) resonating beam placed diagonally on the island in a square diaphragm made of silicon. Aluminum nitride (AlN) thin films deposited at the extreme ends of the SIN beam is used for resonant actuation and sensing. Customized process steps are followed with seven masks to fabricate the sensor, which is first of its kind in the fabrication of microresonant pressure sensors with AlN as piezoelectric material for sensing and actuating the resonating beam. Basic mechanical and electrical characterization is carried out on the unit devices individually to identify the resonance characteristics of the sensor. The results obtained from numerical simulations and experimentation are in close agreement and in the same dimensional range. Closed loop electronics are also designed and tested to vibrate the resonating beam of the unit device at its resonant frequency under no pressure load conditions, which is found to be close to the measured resonance frequency from the mechanical characterization.