Mass Fabrication of 3D Silicon Nano-/Microstructures by Fab-Free Process Using Tip-Based Lithography.

Methods for the mass fabrication of 3D silicon (Si) microstructures with a 100 nm resolution are developed using scanning probe lithography (SPL) combined with metal-assisted chemical etching (MACE). Protruding Si structures, including Si nanowires of over 10 µm in length and atypical shaped Si nano- and micropillars, are obtained via the MACE of a patterned gold film (negative tone) on Si substrates by dip-pen nanolithography (DPN) with polymer or by nanoshaving alkanethiol self-assembled monolayers (SAMs). Furthermore, recessed Si structures with arbitrary patterning and channels less than 160 nm wide and hundreds of nanometers in depth are obtained via the MACE of a patterned gold film (positive tone) on Si substrates by alkanethiol DPN. As an example of applications using protruded Si structures, nanoimprinting in an area of up to a centimeter is demonstrated through 1D and 2D SPL combined with MACE. Similarly, submicrometer polydimethylsiloxane (PDMS) stamps are employed over millimeter-scale areas for applications using recessed Si structures. In particular, the mass production of arbitrarily shaped Si microparticles at submicrometer resolution is developed using silicon-on-insulator substrates, as demonstrated using optical microresonators, surface-enhanced Raman scattering templates, and smart microparticles for fluorescence signal coding.