Mechanical fatigue fracture of silicon - Potential dander to the reliability of silicon MEMS structures

Silicon and polysilicon are both susceptible to fatigue. It might have been once believed in the beginning of micro electro-mechanical systems (MEMS) technology that silicon is a brittle material with almost unlimited fatigue lifetime. However, recent researches revealed many evidences of fatigue fracture, which is potentially a serious threat for the reliability of MEMS structures Although many MEMS devices are often operated at high frequencies with relatively large stress levels, mechanical fatigue behavior of silicon is one of the most unfamiliar issues in mechanical engineering. While MEMS expands its frontier towards medical and aerospace applications for example, where structural failure leads to immediate danger, knowledge accumulated so far about the fatigue properties of silicon is still quite limited. Even the fundamental mechanism of fatigue is now under intensive debate. Up-to-date information of this hot issue is shared in the presentation, looking for a physical image of fatigue process and statistical evaluation of long term reliability in order to push further forward the possibility of silicon-based microtechnologies.