Nanocantilever based mass sensor integrated with CMOS circuitry

Abstract

We have demonstrated the successful integration of a cantilever based mass detector with standard CMOS circuitry. The purpose of the circuitry is to facilitate the readout of the cantilever's deflection in order to measure resonant frequency shifts of the cantilever. The principle and design of the mass detector are presented showing that miniaturization of such cantilever based resonant devices leads to highly sensitive mass sensors, which have the potential to detect single molecules. The design of the readout circuitry used for the first electrical characterization of an integrated cantilever is described in detail. The integration of the cantilever is a post processing module and the full process sequence is discussed. One of the main challenges during the fabrication of the cantilevers is sticktion of the cantilever to the bottom substrate after underclothing. Two dry release techniques were used to solve the problem, namely freeze-drying and resist-assisted release. The fabrication results of cantilevers defined by laser and E-beam lithography are shown. Finally, an AFM based characterization setup is presented and the electrical characterization of a laser-defined cantilever fully integrated with CMOS circuitry is demonstrated. The electrical characterization of the device shows that the resonant behavior of the cantilever depends on the applied voltages, which corresponds to theory.