Electrical breakdown phenomena for devices with micron separations

The electric breakdown of gaseous dielectrics predicted by Paschen's law has been successfully employed for the design of insulation among metallic conductors separated by millimeter scale gaps or larger. However, today most electrostatic actuated MEMS devices have been designed and fabricated with micron-scale gaps that lead to a high risk of failure. Paschen's curves measured under macro or meso gaps hereby must be re-examined and carefully evaluated for providing the guidelines of insulation design in MEMS devices. In this paper, geometric configurations commonly employed for MEMS electrodes, typically planar and inter-digitated combs, have been designed and analyzed with commercial software packages. For verification purposes, breakdown voltages were measured on test samples fabricated with metallic, p-type and n-type silicon substrates in standard MEMS processes. The samples were prepared by etching insulation gaps measured from 2 to 21 mu m. In conclusion, Paschen's curves for describing the electric breakdown phenomena of gaseous dielectrics were revisited and compared to the published data so that design guidelines of electrical insulation in MEMS actuators are established.