Strength predictions for interlocking microridges fabricated with different geometries

This paper analytically evaluates the strength of microcomponents fabricated using both wet and dry etching techniques. A finite element model (nanometer meshed) coupled with a macroscopically accepted energy criterion is used to predict the strength of four different microridge structures (geometries). Agreement between analytical predictions and experimental data on single crystal silicon is excellent and validates the use of macroscopic models to predict the strength of micromachined components fabricated with a wide range of processes. The model is used to evaluate design parameters such as the influence of height and ridge material on strength properties. The analytical portion of the study suggests that optimum ridge height exists to maximize the strength and by choosing tougher materials, the strength of the ridges may be improved by an order of magnitude. However, the significant strength improvement is not validated experimentally. The simulation results confirm that the geometries rather than etching flaws are critical issues when dealing with strength of micromachined components. Furthermore, standard macroscopic methods can be used to predict the strength of MEMS components at the micron size level.