Planarization for three-dimensional photonic crystals and other multi-level nanoscalestructures

Abstract

We describe an approach for achieving local as well as global planarization in the fabrication ofmulti-level nanoscale structures. Using a ‘pre-fill-in’ technique, where trenches are filled withSiO2 prior to the application of a planarizing liquid, we demonstrate thatthe global degree of planarization can be improved from a mere∼25% toover ∼90%. The first layer of a woodpile photonic lattice with a period of∼0.5 µm and a minimumfeature size of ∼0.2 µm is used as an example structure to illustrate the issues involved in planarization. Thismethod provides an attractive and simpler alternative to the traditional chemicalmechanical polishing approach, which can be quite complicated at nanoscale featuresinvolving non-traditional materials.