Effects of elevated temperature treatments in microstructure release procedures

Elevated temperature solvent rinses are shown to reduce stiction of micromechanical structures after release etch processing. Rinsing the structures in boiling methanol after rinsing in water significantly improves yields. Photographs taken during the drying process indicate two distinct modes of solvent vaporization, one of which leads to stiction. This process can be modeled and used to predict the critical length of cantilevered beams above which stiction occurs. A key element of this model is that the dynamics of the drying process are strongly influenced by the shape of the microstructure perimeter. The decrease in stiction cannot be explained solely by liquid bridging modeling in case of elevated rinse temperature. Stiction can be further decreased by drying at high temperature in a rapid thermal annealer; this suggests that instability of the trapped liquid under tension at elevated temperatures may be a dominant factor in reducing the stiction