A physical model to predict stiction in MEMS

One of the most important reliability problems in micro-electromechanical systems (MEMSs) is stiction, the adhesion of contacting surfaces due to surface forces. After reviewing the known physical theory, and the measurement method commonly used to investigate stiction, we present a model that can be used to investigate the sensitivity of MEMS to stiction. It quantitatively predicts the surface interaction energy of surfaces in contact. Included in the model is the roughness of the contacting surfaces and the environmental conditions (humidity and temperature). This is done by describing the surface interaction energy as a function of the distance between the surfaces. This distance is not a unique number, but rather a distribution of distances. It is shown that, if we know this distribution, we can calculate the surface interaction energy. The model is suitable for the prediction of forces due to capillary condensation and molecular interactions.