Dynamical imaging of MEMS devices at sub-micrometer scale using time-resolved scanning electron microscopy.

Present MEMS characterization rests mostly on separated time and space information. In this contribution, we present MEMS morphological imaging by time-resolved scanning electron microscopy, with simultaneous sub-micrometric and sub-microsecond resolution. MEMS devices are actuated close to their resonant frequencies and imaged by a pulsed electron beam probe, generated by beam blanker slicing. The time delay between the periodic actuation voltage and the electron pulse landing is kept constant during the acquisition of secondary electron images. MEMS stroboscopic motion movies are obtained by the sequential acquisition of images over an equispaced mesh of delay times. The technique provides unprecedented local in plane point-by-point trajectory information, potentially allowing the time-resolved characterization of oscillatory modes, local strain and stress, structural deformations and defects, and nonlinear effects. We will further focus on the present limits of the technique, mostly related to the e-beam induced charging. We will discuss strategies to mitigate these instrumental artifacts, improving space and time resolution performances towards the nanometer and ultrafast time scale.