Prediction of strength and fatigue lifetime of MEMS structures with arbitrary shapes

Strength and fatigue lifetime of polycrystalline silicon thin films with notches were successfully predicted from the information obtained from reference specimens with uniform stress distribution. The initial damage, which was induced by patterning process and supposed to be independent of specimen shapes, was characterized as an equivalent crack distribution from the strength distribution of reference specimens. Static strength of notched specimens was then estimated from a statistical point of view with stress distribution taken into account. Fatigue lifetime was estimated on the basis of fatigue crack extension process described by Paris´ law, with the two parameters obtained from uniform stress specimens in the previous study as material inherent constants.