Methods of polymer deposition for forming reduced critical dimensions are described. In one embodiment, a substrate is provided into a chamber, the substrate having a patterned layer disposed on an underlying layer formed thereon. The patterned layer includes a plurality of openings, each opening having a sidewall, a bottom, and a critical dimension. A gas mixture is provided into the chamber, the gas mixture having an etching gas and a polymer control gas. The polymer control gas includes a polymerizing fluorocarbon CxFy gas and a C—H bond containing gas. A plasma is formed with the gas mixture and a conformal polymer layer is deposited in the presence of the plasma on the patterned layer to form a reduced critical dimension in each opening. The reduced critical dimension is smaller than the corresponding critical dimension of the opening.