Out-of-Plane MEMS Actuation Using a Scanning Electron Microscope

In the world of micro-electromechanical systems (MEMS) R&D efforts are expended creating new means of actuation, usually trading either force or displacement. In our scheme we pump charge into an electrically isolated conductive system with a Scanning Electron Microscope (SEM) to achieve a net force away from the substrate. Though we observe a highly dynamic response, we have approximated the force of the system with a quasi-static mechanical force sensor. The study of this actuation has focused on a spiral spring fabricated in Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT-V™). Experiments show the effect of SEM beam conditions on this device, most notably finding the operation to begin at 5 keV accelerating voltage, where our Monte Carlo simulation predicts the beam will begin penetrating the 0.3 μm thick polySi. The out-of-plane motion has been measured as high as 220 μm which is approximately 2/3 of the diameter of the 2D spiral. A linear elastic model of the force sensor shows that in mechanical equilibrium the deflection is associated with an equivalent uniform pressure up to 90 Pa.