Pressure Sensitive Aluminum Nitride Drumhead Resonators

This work reports on the highly-sensitive frequency modulation of a piezoelectrically-actuated Aluminum Nitride (AlN) resonant pressure sensor. We show that the resonance frequency of a drumhead mode with a 300 nm cavity, in pressure equilibrium with the ambient environment, linearly increases with increasing pressure up to 33kPa. The membrane stiffening with increased ambient pressure is due to the added restoring force applied to the membrane by the gas trapped in the cavity. Experimental results show that the resonance frequency linearly increases from 3.66 MHz to 3.72 MHz as the pressure increases from 500 Pa to 33 kPa, resulting in a f vs. p sensitivity of 0.5 ppm/Pa. By eliminating the need for a vacuum or stable reference cavity common in differential pressure sensors, our absolute pressure sensor is a more reliable candidate for long-term measurements, static and dynamic pressures and under high pressure loads.