Interfacial Adhesion between Rough Surfaces of Polycrystalline Silicon and Its Implications for M/NEMS Technology

摘要

An electrostatically actuated double-clamped cantilever beam test structure has been designed and fabricated to determine the adhesion forces between co-planar, impacting polycrystalline silicon (polysilicon) surfaces. To examine the effect of apparent contact area, dimples of varying sizes have been included in the test structure. By measuring the cantilever beam profile, through optical interferometric methods, as a function of applied bias, the force of adhesion has been determined for various device geometries. The results reveal a weak dependence of adhesion on apparent contact area, rather than a linear dependence. Fabrication process artifacts, observed and discussed here, contribute to but do not suffice to explain this observed weak scaling. The results strongly suggest that contact on the micrometer scale between rough, rigid materials such as polysilicon involves only a few asperities.