Directed self-assembly of a high-chi block copolymer for the fabrication of optical nanoresonators

In this paper, we report on the fabrication of optical nanoresonators using block copolymer lithography. The nanostructured gratings or nanofins were fabricated using a silicon-containing block copolymer on a chromium coated silicon-on-insulator substrate. The etch resistance of the block copolymer template enables a unique patterning technique for high-aspect-ratio silicon nanofins. Integration of the directed self-assembly with nanoimprint lithography provides a well-aligned array of nanofins with a depth of ∼125 nm on a wafer scale. The developed nanopatterning method is an alternative to the previously reported nanopatterning techniques utilizing block copolymers. A dense array of sub-10 nm nanofins is used to realize a photonic guided-mode resonance filter. The nanostructured grating provides high sensitivity in refractive index sensing, as demonstrated by simulations and experiments in measuring varying contents of the tetrahydrofuran solvent.