A method of pattern etching a Si-containing anti-reflective coating (ARC) layer is described. The method comprises etching a feature pattern into the silicon-containing ARC layer using plasma formed from a process gas containing SF6 and a hydrocarbon gas. The method further comprises adjusting a flow rate of the hydrocarbon gas relative to a flow rate of the SF6 to reduce a CD bias between a final CD for nested structures in the feature pattern and a final CD for isolated structures in the feature pattern.