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Fabrication of Photonic Crystals Consisting of Si Nanopillars by Plasma Etching Using Self-Formed Masks

We fabricated two dimensional photonic crystals (a square and a triangular lattice) with a photonic band gap (PBG) in the visible light range by periodically arranging Si nanopillars with a period of 270 nm. The pillar diameter and height are 50 nm and 1 µm, respectively. The fabrication process uses iron clusters as nuclei for self-formation of etching masks during electron cyclotron plasma etching with SF6 gas at -135°C to obtain high-aspect-ratio Si nanopillars. The iron clusters are arranged by electron beam lithography. The reflection spectra of the square lattice photonic crystal have a peak around 570 nm for transverse magnetic polarization light while that for transverse electric polarization have a peak around 550 nm. This is consistent with our theoretical calculation that the photonic crystal has a PBG at these wavelengths.