Investigations on Nonlinearities of Roof Tile-Shape Modes for Pressure Measurement Applications

This paper investigates the utilization of MEMS oscillators for absolute pressure measurement applications. For this purpose, the resonance behavior of piezoelectrically (AlN) driven micro-oscillators is characterized. The focus of this work is on so-called roof tile-shape (RTS) modes which exhibit a strong nonlinearity. These eigenmodes are investigated experimentally for two cantilever structures and for three AlN-layer coverage areas (33, 50, and 100 %), depending on the ambient pressure ranging from 10
⁻³
to 10
³
mbar. As a special feature related to a Duffing oscillator, nonlinear spring softening and spring hardening effects occur, depending on the size of the coverage. For the evaluation, the frequency shift of the peak amplitude and the frequency hysteresis are presented as two quantities, which correlate well with the ambient pressure.