Plasma fluorination of diamond-like carbon surfaces: mechanism and application to nanoimprint lithography

摘要

Diamond-like carbon (DLC) films, used as molds for nanoimprint lithography, were treated with a fluorocarbon-based plasma in order to enhance their anti-adhesion properties. While ellipsometry and atomic force microscope measurements showed negligible changes in thickness and surface roughness after plasma processing, contact angle measurement found fluorine plasma-treated DLC surfaces to be highly hydrophobic, with surface,energy values reduced from __45 mJ m~(-2) for untreated films to __20-30 mJ m-2 after fluorination. X-ray photoelectron spectroscopy revealed a thin (from __0.5 to __3 nm) fluorocarbon layer on the DLC surface. Proposed mechanisms for the formation of this layer include two competing processes: etching of DLC and deposition of fluorocarbon material, with one or the other mechanism dominant, depending on the plasma conditions. Fluorocarbon plasma-treated DLC molds for nanoimprint lithography were used to pattern sub-20 nm size features with a high degree of repeatability, demonstrating an extended lifetime of the anti-adhesion coating.