Sub-20 nm Si fins with high aspect ratio via pattern transfer using fullerene-based spin-on-carbon hard masks

We report on a novel and simple pattern transfer process into Si via fullerene-based spin-on-carbon (SOC) hard masks in this work. Electron beam lithography and extreme ultraviolet interference lithography techniques are used to pattern high-resolution and dense lines on a resist/SOC bilayer. The patterns are subsequently transferred by a low-pressure O-2 plasma etching (SOC) and reactive ion etching process with a gas mixture of SF6 and C4F8 (Si). Si sidewall trimming can be controlled by modifying the Si etching rate, achieving Si fins with dimension down to 15 nm half-pitch with aspect ratio as high as of 7:1.