3D nanostructures by combined FIB and electron beam processing

The further miniaturization of silicon sensor and actuator devices using highly developed semiconductor technology at the micro- and nanometer level will lead to a new generation of nano-electro-mechanical systems (NEMS). In the contribution a NEMS fabrication technique will be presented which combines high concentration p-type doping of silicon by high resolution writing focused ion beam (FIB) implantation and subsequent anisotropic and selective wet chemical etching. FIB-patterned and chemically etched 3D Si structures with nanoscale features have been fabricated using 30 keV Ga+ ion implantation (CANION 31Mplus) into silicon-on insulator (SOI) device layers followed by an anisotropic etching in KOH/H2O solution [1]. This technology is combined with classical microelectronic techniques, like lithography and broad beam implantation working on a 4 inch wafer to increase the fabrication efficiency especially for the contact areas. Fabrication considerations to achieve free-standing Si nanostructures, like nanowires nanobridges, see Fig. 1, nanocantilevers etc., are discussed and some typical nanostructures with potential NEMS applications, for example as nano-thermometer, gas sensors or solid-state vacuum nano-triodes, see Fig. 2, are shown. Because the selectively etched free-standing nanobeams are in a highly Ga-doped amorphous state their electrical resistance is quite large. For reduction of the beam resistance they were covered with a metal film using electron beam assisted deposition of a 30 nm Pt layer.
Finally, results of temperature-dependent resistance measurements on nanowires, of AC voltage excited nanobeam deflection measurements and of measurements on vacuum nano-triodes are presented, showing the potential for future device applications.