New failure mechanism in silicon nitride resonators

Abstract

This study focuses on a new reliability problem of micromechanical structures based on thin silicon nitride films. Silicon nitride is used in numerous MEMS applications thanks to its good mechanical and electrical properties. The SiN/sub x/ micromechanical structures usually serve as supporting elements such as membranes, plates and cantilevers. A new failure mechanism is found in thin resonating SiN/sub x/ structures operating in air. The stiffness of the structure is changing due to surface oxidation. The surface oxide layer can crack and recover during operation of the device. This results in unstable resonance frequency and failure of the resonant mode MEMS device.