A system for automatic electrical and optical characterization of microelectromechanical devices

A new optical method for characterizing the performance of microelectromechanical systems (MEMS) is described that is significantly faster and simpler than previously described optical methods. The method uses video imaging under continuous illumination to effectively remove the upper limit imposed by other methods on the frequency of motions that can be measured. It can be used to measure the motions of any visible structure, whether or not an electrical or optical sensor for that motion has been incorporated. The magnitude of the displacement of a target, such as the edge of a sinusoidally vibrating shuttle mass, is obtained from a single frame of video taken during motion plus a reference frame taken when the target is at rest. The speed of this technique facilitates hands-on testing of prototypes and is especially attractive for production environments. An automated MEMS microresonator testbed is described that performs on-line resonance curve parameter extractions of resonant frequency (f₀) and quality factor (Q) from electrical measurements, which are derived from output comb-drive current measurements using established methods, and from simultaneous optical measurements using the new method. Results obtained using these methods for design evaluation of microfabricated lateral resonators are discussed, and favorable benchmark comparisons of the optical results with results from a MEMS testbed at the Massachusetts Institute of Technology are presented