Effects of fabrication error on the pull-in voltage of capacitive micro accelerometer

Dimension uncertainty inevitably occurs in almost every fabrication of microstructure because of its small size and ununiformity of material, therefore, the dimension error is a significant factor to be considered in MEMS structure design. The unsymmetrical gaps of capacitors induced by processing are selected to analyze the effects of error on the pull-in voltage of capacitive microaccelerometer. Analytical method is used to construct the force balance equation as the mass located in different position under different types of errors, and corresponding graphs are given to study the relation between pull-in voltage and fabrication error. The notation of stiffness ratio R is introduced to simplify the process of analyzing; the maximum of R determines the maximum electrostatic stiffness, which is quadric relation to the maximum voltage could be applied. Finally, the analytic result and simulation result are presented to show the effects of error on pull-in voltage, and both results have the same trend and are almost equal to each other.