Adhesive contact of axisymmetric suspended miniature structure

Abstract

Strong adhesive force between two solid surfaces is in some cases sufficient to deform a miniature structure to a substrate resulting in the stiction failure of microelectromechanical systems (MEMS) devices. Using linear elastic plate theory and considering the influence of internal tensile stresses, the deflection and adhesive contact of an axisymmetric suspended miniature structure are analyzed. The contact between the miniature structure and the substrate is divided into two separate stages: (1) without adhesion, (2) with adhesion. Without adhesion, the load required to deform the miniature structure increases with the internal tensile stresses and the contact area. For adhesive contact, a thermodynamic method is used to analytically obtain the pull-off force required to separate the miniature structure from the substrate. The pull-off force increases with the contact area and the bonding strength between two solid surfaces and decreases with the internal tensile stresses. To predict stiction, a criterion on the geometry of the miniature structure as a function of adhesion energy, internal tensile stresses and contact area between the miniature structure and the substrate is established, which can be used to improve the MEMS design and prevent the sticking failure.