Cantilever tip probe arrays for simultaneous SECM and AFM analysis

A cantilever transducer system with platinum tip electrodes in sub-micron regime has been fabricated for simultaneous Scanning Electrochemical Microscopy (SECM) and Atomic Force Microscopy (AFM) analysis. Sharpened High Aspect Ratio Silicon (HARS) tips are shaped combining isotropic and anisotropic deep-reactive etch processes and form the body of the transducer. Deposition of a silicon nitride followed by a back etch step allows embedding these silicon tips in a silicon nitride layer so that they protrude through the nitride. This way, embedded silicon tips with a diameter smaller than 600 nm, a radius smaller than 50 nm, and an aspect ratio higher than 20 can be achieved. Subsequently, a platinum layer and an insulator layer are deposited on these tip structures. Introducing a metal masking technology utilizing Focused Ion Beam (FIB) technology, a precise exposure of the buried metal layer can be achieved to form ultra micro-electrodes on top of the tip. Finally, cantilever structures are shaped and released by etching the silicon substrate from the backside. Electrochemical and mechanical characterization show full functionality of the transducer system. Due to the high aspect ratio topography of the tip structure and low spring constant of silicon nitride cantilevers, these probes are particularly suited for high resolution SECM and AFM analysis. Furthermore, this technology allows a production of both linear probe arrays and two-dimensional probe arrays.

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