Study on dielectric charging in low-stress silicon nitride with the MIS structure for reliable MEMS applications

Charge-induced failure has been recognized as a primary reliability issue in capacitive micro-actuators. In this paper, we present a simple method to assess the effect of dielectric charging on reliability of a capacitive micro-actuator. By capacitance–voltage measurements for a metal–insulator–semiconductor (MIS) structure, the characteristics of dielectric charging can be investigated, and the obtained results can be used to study the charging behavior of a capacitive micro-actuator. An analytical model based on this method has been established. The silicon-rich nitride film was deposited by low-pressure chemical vapor deposition on silicon substrate. The current–voltage and capacitance–voltage measurements exhibit an asymmetric electrical characteristic under different polarity of stress voltage. The charging parameters of the silicon-rich nitride were extracted by the stretched exponential curve fitting method. This charging behavior suggests that silicon-rich nitride can be negatively or positively charged, and the injection and transport of holes are more favored than the injection and transport of electrons. The charge injection from movable electrode plays a dominant role in the dielectric charging of a capacitive micro-actuator. It is expected that the charge accumulation in dielectrics can be eliminated by employing the bipolar square-wave voltage to actuate a capacitive micro-actuator.