Fabrication and characterization of nanoresonating devices for mass detection

Abstract

We report on a novel fabrication process and preliminary characterization of a nanomechanical resonating device, which is to be used for mass detection. The fabrication of the device is based on laser lithography on Al coated ${\mathrm{SiO}}_{\mathrm{2}}{\mathrm{/p}}^{\mathrm{++}}{\mathrm{Si/SiO}}_{\mathrm{2}}\mathrm{/Si}$ structures, followed by dry and wet etching. We have fabricated highly doped polysilicon free-hanging cantilevers and anchored drivers for lateral cantilever vibration, where the motion of the cantilever is parallel to the substrate. The cantilevers are actuated electrically by applying an ac voltage between the cantilever and driver. The laterally vibrating cantilever structures are approximately 30–50 μm in length, 1.8 μm in height, and 500 nm in width. The characterization of the resonators was performed by direct observation of the cantilever through an optical microscope. An electrical measuring technique is also presented and discussed. Typical values of resonant frequency and quality factor, at 1 atm, are approximately 500 kHz and 50, respectively. Moreover, a dependence of the resonant frequency on the applied dc voltage between the cantilever and driver has been found.