Stiction failure of micro-structure in hermetic packaging

Hermetic packaging is introduced as a main mode for the MEMS (micro-electromechanical-system) device packaging. The reliability of micro-structures in hermetic packaging has become the most important part for the successful commercialization. With the decrease in the dimension and material processing, the ubiquitous surface effect between device and substrate has become more and more effective. Surface-micromachined structures formed by the wet etching of sacrificial layers are commonly plagued by problems of sticking to the substrate. The failure of devices according to the stiction has become a main factor of the MEMS reliability. In this paper, an experimental way is presented to analyze two important force of surface effect: capillary force and van der Waals force. The cantilever beam is used as a classic MEMS device, and the structure of beam is specially designed for the experiment. It can greatly reduce the capillary force in a vacuum environment, so the two forces are separated through two different environmental experiments. This paper simulates different packaging environments to separate capillary force from stiction force, and analyzes the composition of the stiction force. The experimental results and theoretical summary could provide a useful reference for the design and predict the stiction failure of micro-structures.