Mechanical behavior of ultrathin microcantilever

Mechanical characteristics of a single crystal silicon ultrathin cantilever and their dependence on the geometry was investigated in this paper. The cantilevers with thickness 60 and 170 nm and length 5-120 μm have been fabricated from 〈100〉-oriented SIMOX wafer. Preliminary results show that the longer cantilevers (L>30 μm) have higher mechanical quality factor, Q (>10⁴) than the shorter ones (L<30 μm), since the shorter one is more susceptible to the energy loss, i.e., support loss and surface loss (oxide layer). Furthermore, multimode resonance of the longer cantilever was observable within the measurable range, and all of them have the Q factor higher than 10⁴. By using the high resonance mode, these cantilevers are theoretically capable of detecting the force as small as 2×10^-17 N. In addition, the atomic scale mass resolution (1.4×10^-22 g) is also expected by these cantilevers if it is used for sensing the mass load. Using the dynamic detection method, water vapor adsorption was detected, and the mass resolution of the cantilever is roughly estimated to be 2.9×10^-17 g.