Detection of stiction of suspending structures in MEMS by A Laser Doppler Vibrometer systems

Abstract

Stiction as one of the most failures both in MEMS fabrication and operation has been widely studied. With the decrease in the dimension and material, the ubiquitous surface effect between the 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. This paper presents a useful diagnosis system for fully detecting and characterizing the stiction failure occurring in MEMS. The system consists of an LDV (laser Doppler vibrometer), a chamber with controllable environment such as pressure and temperature, and a diagnosis program developed by Matlab software. Full knowledge about the stiction, including its position, shape, stiction releasing configuration and probability of re-stiction can be accessed using the system. We also present an experimental way to analyze two important forces of the surface effect: the capillary force and the van der Waals force. The experimental diagnosis methodology and theoretical summary could provide a useful reference for detecting and predicting the stiction failure of micro-structures.