This work demonstrated the ability to transfer a nanoscale 3-D polynomial structure of arbitrary shape into Si with a single step electron-beam lithography process. The technique involved employing a proximity correction algorithm, PYRAMID, to derive the dose distribution for a given 3-D structure by accounting for the electron scattering effects of the surrounding pixels. The pattern was written into a polymethyl methacrylate (PMMA) resist and then successively transferred into Si via reactive ion etching, where a 1:1 etching ratio between PMMA and Si was achieved. The pattern transferred into Si possessed nanoscale features and matched the desired pattern with high fidelity.
Microcantilever based sensors have been being widely used for measuring or detecting various physical conditions, chemical agents and biological species. Researchers are continuing to focus on enhancing the sensitivity of these devices toward improving their performance and applicability. In this paper, a numerical study is performed to assess the influence of microcantilever geometry on sensitivity to improve these devices for better detection of hazardous biological agents in liquid environments. Modal analyses were performed on microcantilevers of different geometries and shapes using ANSYS software and compared to the basic rectangular shaped microcantilever structures employed by most researchers. These structures all possessed a 50 μm length, 0.5 μm thickness and 25 μm width where the cantilever is clamped to the substrate, and were analyzed for their basic resonance frequency as well as the frequency shift for the attachment of a 0.285 picogram of mass attached on their surfaces. These numerical results are compared for the improvement of the sensitivity for MEMS based microcantilever sensor, which is particularly promising for biosensor applications. Of the geometries studied a few were found to possess a significant increase in mass sensitivity over regular rectangular shaped cantilever beam structures of similar dimensions. In particular, it was found that geometries possessing larger clamping widths and/or reduced effective mass at the free end yielded enhanced sensitivity.
A triangular shape was found to increase mass sensitivity an order of magnitude over standard rectangular shapes.