Determination of the dynamics of micromachined lateral suspensions in the scanning electron microscope

A lateral suspension, suitable for a microseismometer application, has been fabricated using deep reactive-ion etching. The critical dynamic parameters of the suspension, namely the normal modes along the compliant axis and the damping, have been determined from slow-scan imaging in an environmental scanning electron microscope. The results show the presence of an unwanted spurious mode which can be attributed to the finite mass of the suspension. An analytical solution yields good agreement with observations. Damping is shown to be dominated by viscous effects, with the suspension material only limiting performance at high vacuum.