Etching for Vertical Sidewall Formation in TiO₂ Nanorods

Abstract

Titanium dioxide (TiO 2 ) is a desired material for visible light applications owing to its relatively low absorption coefficient and high refractive index compared to those of silicon dioxide (SiO 2 ) and silicon nitride (Si 3 N 4 ), which are standard CMOS-compatible materials. Since the recent emergence of metasurfaces operating in the visible region, the dry etching of TiO 2 has become crucial for fabricating nanostructures with subwavelength scales. In this study, we investigated dry etching conditions for the fabrication of TiO 2 nanorods with vertical sidewalls while changing the gas combination of Ar/Cl 2 and Ar/BCl 3 and adding HBr in small amounts. By measuring the sidewall angle of TiO 2 nanorods etched under several etching conditions, we determined a suitable etching condition to form a sidewall with an angle of 89 ∘ .