Adhesion Limits and Design Criteria for Nanorelays

Microelectromechanical switches are of interest for low-power circuit applications due to their minimal OFF state leakage current. This paper uses 22-nm CMOS fabrication technology and the clamped cantilever geometry as the basis for establishing design rules for electrostatic nanorelays and estimates the design parameters needed for nanorelay actuation. The adhesive pull-off force of various substrate/cantilever combinations is simulated using molecular dynamics with a force field that parameterizes van der Waals interactions, and measured using atomic force microscopy. Both methods show that for the substrates studied, H-passivated Si produces the least adhesive surface with adhesive pressure close to the critical pressure required for pull-out. Experimental results quantifying adhesion and electrical current conduction show that it is impossible to simultaneously meet the adhesion and current conduction requirements of a nanorelay. We show that contact adhesion is the key parameter limiting the scalability of electromechanical relays at the nanoscale.