Modeling of Wet Stiction in Microelectromechanical Systems (MEMS)

Stiction, which is a term commonly used in micro-electromechanical systems (MEMS) to refer to adhesion, is a major failure mode in MEMS. Undesirable stiction, which results from the contact between surfaces, can severely compromise the reliability of MEMS. In this paper, a model is developed for predicting stiction between uncharged micro parts interacting in a humid environment. In this condition, for hydrophilic surfaces, the capillary and asperity deformation forces are dominant. Here, using a newly developed multiple asperity contact model, a model is developed for the capillary force between rough micro surfaces, and the new model is combined with a newly developed elastic/plastic deformation model for rough surfaces to solve for the equilibrium of the forces. This in turn yields the equilibrium distance between micro surfaces using which the apparent work of adhesion can be found. The theoretical results are compared with the available experimental data from literature. The developed model can be easily used for design purposes. If the topographic data and material constants are known, the desirable adhesion parameters can be quickly found from the model.