Methods and apparatus for in-situ protection liners for high aspect ratio reactive ion etching

Methods and apparatus for producing high aspect ratio features in a substrate using reactive ion etching. In some embodiments, a method comprises flowing acetylene gas into a process chamber to produce a diamond like carbon deposition on a pattern mask or on at least one layer of oxide or nitride on the substrate, flowing a gas mixture of a first gas of a hydrofluorocarbon-based gas and a second gas of a fluorocarbon-based gas into the process chamber, forming a plasma from the gas mixture using an RF power source and at least one RF bias power source, performing an anisotropic etch of the at least one layer of oxide or nitride on the substrate using the pattern mask, and evacuating the process chamber while interrupting the RF power source to stop plasma formation.