Abstract
During the process of designing capacitive microelectromechanical systems (MEMS) it is necessary to calculate electric capacitance and electrostatic forces acting between different elements of the construction. These parameters are often evaluated using analytical expressions which do not take into account fringing field effects or by means of numerical computation which takes into account these effects but requires a lot of time and powerful computers that hamper further optimization. At initial stages of MEMS design it is essential to have fast, accurate and evident methods of electrostatic interaction calculation. Therefore analytical expressions allowing evaluating capacitances and electrostatic forces with an accuracy sufficient for practical application are of great interest. This work is devoted to experimental and theoretical study of electrostatic interactions in parallel-plate MEMS within a 3D-approach. Dependences of capacitance and electrostatic forces on the interelectrode gap, electrode thickness, and the length-to-width ratio are calculated using the finite element method. On the basis of the calculation approximation formulas for capacitance and electrostatic forces evaluation taking into account fringing field effects have been obtained. A comparison between experimental and theoretical results demonstrates a good coincidence. Applicability limits of the formulas obtained with regard to fringing field effects within 3D, 2D, and 1D-approaches are estimated.
Keywords: MEMS, parallel-plate capacitor, capacitance, electrostatic forces, fringing field effects, finite element method, approximation formulas