Fabrication of nanoelectromechanical systems in single crystal silicon using silicon on insulator substrates and electron beam lithography

We have demonstrated a process for fabricating nanometer-scale electromechanical structures of diverse geometries in single crystal silicon, using silicon on insulator substrates. We pattern the substrate using high resolution electron beam lithography with 100 keV electrons followed by Al evaporation and liftoff. The Al is used as an etch mask in CF₄ reactive ion etching to pattern the top silicon layer. We then undercut structures using a buffered oxide etch. The structures were made from substrates having a top silicon thickness of 200 or 50 nm, and a buried oxide thickness of 400 nm. With this process we have made a variety of movable structures. We describe the performance of an electrostatically driven Fabry-Perot interferometer that consists of a μm sized pad suspended by wires that are 100-200 nm wide. We have also made much smaller mechanical structures such as suspended silicon beams as narrow as 30 nm.