A method of patterning a silicon containing ARC (anti-reflective coating) layer underlying a patterned layer is described that includes establishing a flow of a process gas to a plasma processing system, selecting a process condition that increases an etch selectivity of the silicon containing ARC layer relative to the patterned layer, igniting plasma from the process gas using a plasma source in accordance with the process condition, and exposing the substrate to the plasma to extend the feature pattern of the patterned layer into the silicon containing ARC layer. The composition of the process gas and the flow rate(s) of the gaseous constituents in the process gas are selected to adjust the carbon-fluorine content.