Cryogenic etching of nano-scale silicon trenches with resist masks

Cryogenic silicon etching using SF6-O2 at the sub-50 nm scale has been developed for nano-electromechanical systems (NEMS) and nano-photonics systems where high aspect ratio trenches are desired. It was found that the SF6-O2 chemistry at cryogenic temperatures (-100 to -130^oC) provides the best combination of etch rate, selectivity, and profile control for the smallest trenches etched. The profile can be well controlled with aspect ratios on the order of 8:1 for 20nm wide trenches. The various etch parameter trends will be discussed along with methods to achieve the optimal profiles and etch rates.