Measurement of adhesion forces between polycrystalline silicon surfaces via a MEMS double-clamped beam test structure

Abstract

An electrostatically actuated double-clamped beam test structure has been designed and fabricated for the quantitative determination of adhesion forces between two contacting polycrystalline silicon (polysilicon) surfaces. The experimental measurements of the beam profile at varied bias and simulations based on finite element methods are combined to evaluate more accurately the adhesion forces experienced between polysilicon surfaces. In particular, the electrostatic force at pull-off is obtained by measuring the pull-off voltage and the beam profile through optical interferometric methods. The adhesion force is then determined from the mechanical restoring force obtained by finite element methods simulations and the calculated electrostatic force. The results show a weak scaling of the adhesion force with the apparent contact area, defined via microfabricated dimples.