  Structuring Si in arrays of vertical high aspect ratio pillars, ranging from
nanoscale to macroscale feature dimensions, is essential for producing
functional interfaces for many applications. Arrays of silicon 3D
nanostructures are needed to realize photonic and phononic crystals,
waveguides, metalenses, X-ray wavefront sensors, detectors, microstructures and
arrays of Si pillars are used as bio-interfaces in neural activity recording,
cell culture, microfluidics, sensing and on-chip manipulation. Here, we present
a new strategy for realizing arrays of protruding sharp Si nanopillars using
displacement Talbot lithography combined with metal-assisted chemical etching
(MacEtch) in gas phase. With the double exposure of a linear grating mask in
orthogonal orientations and the lift-off technique, we realized a catalyst
pattern of holes in a Pt thin film with a period of 1 {\mu}m and hole diameter
in the range of 100-250 nm. MacEtch in gas phase by using vapor HF and oxygen
from air allows to etch arrays of protruding Si nanopillars 200 nm-thick and
aspect ratio in the range of 200 (pillar height/width) with an etching rate up
to 1 {\mu}m/min. With the advantage of no stiction, no ion beam damage of the
Si substrate, nanometric resolution and high fidelity of pattern transfer the
method is an easy-to-scale-up processing that can support the fabrication of Si
pillars arrays for many valuable applications both at micro and nano-scale.
