EFM study of injected charges in the silicon nitride of an electrostatic actuated MEMS

In this paper we introduce an original Electrostatic Force Microscopy (EFM) -based methodology which allows a rapid and easy calculation of the charge density value of electric charges injected in a silicon nitride dielectric layer for conditions which prevail during MEMS switch actuation. The calculation of the number of trapped charges is reproducible and in agreement with the results already published in the literature. A physical model is suggested which describes the charge spot behavior inside the silicon nitride. This model can explain the pull-in voltage shift due to dielectric charging in a RF-switch MEMS.