Etching for Vertical Sidewall Formation in TiO2 Nanorods

Abstract

Titanium dioxide (TiO2) 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 (SiO2) and silicon nitride (Si3 N4), which are standard CMOS-compatible materials. Since the recent emergence of metasurfaces operating in the visible region, the dry etching of TiO2 has become crucial for fabricating nanostructures with subwavelength scales. In this study, we investigated dry etching conditions for the fabrication of TiO2 nanorods with vertical sidewalls while changing the gas combination of Ar/Cl2 and Ar/BCl3 and adding HBr in small amounts. By measuring the sidewall angle of TiO2 nanorods etched under several etching conditions, we determined a suitable etching condition to form a sidewall with an angle of 89∘.