Effect of Vacuum Package on the Stiction Force of Micro-structure

Abstract

Vacuum packaging is introduced as a main mode for the MEMS (Micro-electronics-Mechanical-System) devices packaging. The reliability of devices in a vacuum package 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, we present an experimental way to analyze the two important force of the surface effect: the capillary force and the van der Waals force. We use the cantilever beam as a classic MEMS device, and the structure of beam is specially designed for the experiment. We believe that it can greatly reduce the capillary force in the vacuum environment, so we separate the two forces through two different environmental experiments. This paper simulates different packaging environment to divide 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-structure.