Abstract Anisotropic high-aspect-ratio silicon oxide etching in the sub-100-nm-diameter domain is a challenge due to lithography and plasma etching difficulties. In this paper, we report oxide-etched holes as narrow as 20 nm radius with an aspect ratio of 5 by utilizing electron beam lithography and reactive ion etching with a resist mask and CHF 3 and Ar gases. The process parameters were optimized for etching vacant columns in oxide. The results were corroborated through Focused Ion Beam/Scanning Electron Microscope. Moreover, we study the effects of pressure, power, and gas ratios on the etch process. Finally, we present a previously unreported phenomenon in oxide etching in which the resist mask etch rate is dramatically reduced over time under certain process conditions, allowing for controlled etching. Graphical Abstract Fig. (a) Time evolution of resist thickness (T) for a certain process (b) SEM cross section of a sample showing etched oxide
Hussain et al. (Wed,) studied this question.