Design, fabrication and characterization of a piezoelectric MEMS diaphragm resonator mass sensor

Abstract

This work reports on the design, fabrication and characterization of a piezoelectrically actuated mass sensor. The sensor utilizes degenerate resonant modes in which one mode is used as a reference to compensate for environmental effects. The project builds on a capacitively driven version of the sensor allowing improvements and challenges surrounding the new design to be assessed in relation to modeling and fabrication. The operational mode of interest showed an average resonant frequency of 7.8 MHz (quality factor of 490), at atmospheric pressure with an electrically recovered signal to noise ratio of 2400:1. The lead zirconate titanate performance yielded a central displacement sensitivity of 1.50 nm V−1, which is in good agreement with the levels predicted in modeling. A small initial split in the degenerate modes was recorded due to fabrication tolerances; however, the devices still exhibited good environmental stability, with a temperature sensitivity of only 11 Hz °C−1. Electroplating of gold onto the sensor surface demonstrated a device mass sensitivity of 12.0 Hz pg−1.