Electrostatic actuated mems for precision AC voltage references
The purpose of this paper is to present results on the design of electrostatic actuated micro- electromechanical systems (MEMS) aiming at developing AC voltage references through mechanical-electrical transduction for electrical metrology and more generally for miniaturized instrumentation. Several test MEMS architectures (targeted AC voltages from 10 V up to 100 V) for the vertical motion have been designed and are under fabrication by an epitaxial silicon on insulator (SOI) surface micromachining process with the aim to investigate the potentialities of the different structures with respect to the geometrical dispersion, the strain sensitivity and the electrical stability.
Advantages of alternative actuating signal for MEMS actuators
In this paper, we report the different advantages of using AC actuating signal for driving MEMS actuators. The study is based upon micro-mirror devices used in scanning or digital mode. In scanning mode, an AC signal can be used to overcome difficulties induced by the high voltages required in electrostatic systems by taking advantage of the double rectifying effect of electrostatic actuation within a second order system. On the other hand, when the pull-in effect is used, charge injection occurs after a long time in the deflected position except when the landing electrodes are electro-statically separated from the control electrodes. An AC signal also eliminates charge injection particularly if a bipolar signal is used. Long term experiments have demonstrated the reliability of such a signal command to avoid injection of electric charges.
Failure predictive model of capacitive RF-MEMS
This paper reports on the investigation of the failure mechanism in capacitive RF-MEMS through an efficient analysis methodology. We demonstrate that the physical origin of the dielectric charging is the leakage current through the RF-MEMS dielectric. To monitor the kinetic of this failure phenomenon, we introduce a useful parameter, which corresponds to the shift rate of the actuation voltages (SRAV) and an appropriate reliability-driven electrical stress parameter, which takes the contact quality between the bridge and the dielectric into account. We finally propose a figure of merit, derived from a predictive model, which quantifies the capacitive RF MEMS reliability and open the door to the prediction of lifetime as well as its optimization and/or acceleration for testing.