Optimal design and fabrication of ITO photonic crystal using e-beam patterned hydrogen silsesquioxane resist

Abstract

In this work, the authors report the design and fabrication of photonic crystals of indium tin oxide (ITO) in the visible range. The structures have been obtained using e-beam lithography combined with inductively coupled plasma reactive ion etching in boron trichloride and chlore plasma. They have particularly studied the effect of the process parameters on the hole features. The triangular lattice configuration consisting of air holes radii of 110 nm with a lattice spacing of 290 nm was successfully transferred through the 300-nm-thick hydrogen silsesquioxane resist mask to the 150 nm-thick ITO layer, achieving smooth and vertical sidewalls. The optical characterization, using an end-fire coupling technique, confirmed the existence of a photonic bandgap over 600–800 nm, which is of a great interest to develop new functionalities based on ITO thin films for laser applications in the visible range.