Contact resistance modeling for NEMS ohmic relays using highly doped SiGe contact material

M. Ramezani, A.H. Tamaddon, S. Severi, K. Vanstreels, K. De Meyer, A. Witvrouw
IMEC, BE

Keywords: NEMS switch, contact resistivity, silicon germanium (SiGe), atomic force microscopy (AFM)

Summary:

The principal goal of this work is to develop a more accurate model for the contact resistance using the real surface profile of the contacting material in comparison to the state-of-the art where the surface is modeled by a collection of identical spherical asperities with a Gaussian distribution for the asperity heights. Using a real distribution is important for nano-scale devices for which, due to low amount of contact force, the number of asperities in contact is limited. The real asperity distribution and height values were determined by AFM (Atomic Force Microscope), which allowed determining the number and shape of asperities coming into contact. By using the hardness and the elastic modulus of the specific material, and the contact area, the contact force on each contact spot can be calculated. The contact resistance could then be determined using the deformation height and type (elastic/plastic), resistivity, contact radius and curvature end radius in the Hertz multi-asperities model.