Measuring the Adhesion Energy between MEMS Structures Using an Adhered Cantilever

The spontaneous stiction of microelectromechanical systems’ (MEMS) elements during fabrication or operation is a serious problem. Capillary or electrostatic forces causing stiction can be excluded, but dispersion forces, due to their fundamental nature, are always present and must be studied in detail. In this paper, these forces are studied experimentally for Si–Au and Si–Ru systems using a test structure: an adhered cantilever. Long (12 mm) and thin (10 µm) cantilevers allow accurate measurements to be taken. This paper discusses in detail the procedure for fabricating cantilevers and a measuring chip. Information about the adhesion energy is extracted from the cantilever’s shape, which is measured by a scanning interferometer. The roughness of the contacting surfaces is carefully studied and the equilibrium average distance between the surfaces during contact is obtained. This paper is of interest not only for MEMS but also provides fundamental knowledge about dispersion forces at short distances, which are inaccessible to other measurement methods.