Fabrication of submicron suspended structures by laser and atomic force microscopy lithography on aluminum combined with reactive ion etching

Abstract

We report a simple fabrication method for suspended submicron silicon and silicon oxide structures. The structures are defined by laser and atomic force microscopy (AFM) writing on a 7-nm-thick aluminum film. For laser writing the minimum obtained linewidth is 500 nm, whereas for AFM it is approximately 100 nm. During AFM writing, aluminum oxide is formed, whereas during laser writing, a compound containing aluminum and silicon is formed. For both processes the nonpatterned aluminum can be dissolved selectively in a wet chemical etch leaving the patterned areas as an etch mask. Alternatively, the aluminum oxide can be etched to form a positive etch mask. Aluminum and aluminum oxide are both excellent etch masks for reactive ion etching (RIE) of silicon and silicon oxide. Hence, by combinations of RIE processes, a variety of structures can be fabricated from the aluminum based masks. To illustrate the flexibility of this technique we demonstrate fabrication of submicron cantilevers and bridges defined in silicon and silicon oxide.