A semi-analytical model for calculating touch-point pressure and pull-in voltage for clamped diaphragms with residual stress

摘要

A closed form model for evaluating touch point pressure and pull-in voltage of clamped square diaphragm with residual stress is proposed. Square diaphragms are used in numerous applications. The design parameters for all these structures are pull-in voltage and/or touchpoint pressure. The materials employed for fabricating diaphragms for these structures are p+ doped silicon, polysilicon, silicon nitride, polyimide etc. All these materials have residual stress, which influences the behavior of the transducer. In addition to this, a capacitive transducer may or may not employ an intervening layer of dielectric on the fixed electrode. Closed form expressions for evaluating touch-point pressure and pull-in voltage have been derived for such a structure by means of semi-analytical model. The method proposed is less complex and less time consuming in comparison with FEM tools.