Electron beam lithography on vertical side faces of micrometer-order Si block

Electron beam (EB) nanolithography on resist films coated on vertical side faces of Si blocks with micrometer-order size is demonstrated. This is achieved by combining the authors' original three-dimensional (3D) EB writing technique with the authors' newly developed low-viscosity resist solution. Resist coating with a 2-butanone/hexane low-viscosity solution enables the authors to uniformly coat a high-resolution EB resist poly(methyl methacrylate) on the vertical side faces of Si blocks. The mechanism of uniform coating on the vertical side faces can be understood by considering the lower viscosity of the authors' resist solution. Moreover, Monte Carlo simulation and experimental 3D EB lithography reveal that dense nanopatterning on opposite side faces of a micrometer-order block with simultaneous development is as attainable as that on a flat substrate. The combination of the resist-coating method and 3D EB writing with ion etching from horizontal directions of substrates is promising for creating 3D nanostructures in semiconductors and thus for 3D nanotechnology.