Effective methods to prevent stiction during post-release-etch processing

The drying of rinse liquids after release-etch processing is analyzed and modeled. The model includes both Laplace pressure forces and surface tension forces. A full three dimensional Laplace equation is considered in the analysis. This model explains two distinct drying modes observed in silicon micromachining. According to the model, the shape of the microstructure periphery plays an important role in the drying process. A simple modification of the device design, which does involve any process changes, significantly improves release yields. We also found that stiction could be reduced significantly by rinsing and drying at elevated temperatures. Instability of trapped liquids under tension at high temperature may be a factor in reducing the stiction. Experimental results for both bulk micromachined cantilevered beams, and surface micromachined doubly clamped beams are presented.