Nanofabrication of high aspect ratio (∼50:1) sub-10 nm silicon nanowires using inductively coupled plasma etching

Abstract

The development of nanofabrication techniques for creating high aspect ratio (∼50:1) sub-10 nm silicon nanowires (SiNWs) with smooth, uniform, and straight vertical sidewalls using an inductively coupled plasma (ICP) etching process at 20 °C is reported. In particular, to improve the quality and flexibility of the pattern transfer process for high aspect ratio SiNWs, hydrogen silsesquioxane, a high-resolution, inorganic, negative-tone resist for electron-beam lithography has been used as both the resist for defining sub-10 nm patterns and the hard mask for etching the underneath silicon material. The effects of SF6/C4F8 gas flow rates, chamber pressure, platen power and ICP power on the etch rate, selectivity, and sidewall profile are investigated. To minimize plasma-induced sidewall damage, moderate plasma excitation power (ICP power of 600 W) and low ion energy (platen power of 6–12 W) were used. Using the optimized etch process at room temperature (20 °C), the authors have successfully fabricated sub-10 nm SiNWs, which have smooth vertical sidewall profile and aspect ratios up to ∼50:1. This optimized etch combined with a controlled thermal oxidation allows the realization of consistent, reproducible, and reliable SiNW devices with nominal widths from 100 nm down to sub-5 nm in silicon on top of SiO2 fabricated on silicon on insulator substrates.