Anisotropic etching of polymer films by high energy (similar to 100s of eV) oxygen atom neutral beams

An inductively coupled high density plasma source was used to generate an e nergetic (100s of eV), high flux (equivalent of similar to 10s mA/cm(2)) ox ygen atom neutral beam. Positive ions were extracted from the plasma and ne utralized by a metal grid with high aspect ratio holes. High rate (up to 0. 6 mum/min), microloading-free, high aspect ratio (up to 5:1) etching of pol ymer with straight sidewalls of sub-0.25 mum features was demonstrated. The polymer etch rate increased with power and showed a shallow maximum with p lasma gas pressure. The etch rate increased roughly as the square root of t he boundary voltage (which controls neutral beam energy), and was independe nt of substrate temperature. The latter observation suggests that spontaneo us etching did not occur. The degree of neutralization of the extracted ion s was estimated to be greater than 99% at the base case conditions used in this work. (C) 2001 American Vacuum Society.