Parasitic charging of dielectric surfaces in capacitive microelectromechanical systems (MEMS)

Silicon dioxide and silicon nitride coatings are preferably used as dielectric layers for short-circuit protection in capacitive silicon microsensors and microactuators. However, their tendency to electrostatic charging can diminish the device reliability. Gas discharges in the air gap of silicon cantilever actuators have been observed, resulting in surface charge accumulation on the electrode passivation of the devices. Charge decay characteristics were recorded for a silicon oxide passivation and a multilayer passivation by silicon oxide and silicon nitride. The charges are found to be highly stable in time. Based on these observations, rules for the application and design of dielectric layers in microdevices are proposed. (C) 1998 Elsevier Science S.A. All rights reserved.