Method for metallizing a pattern in a dielectric film

A method of patterning a film stack is described. The method comprises preparing a film stack on a substrate, wherein the film stack comprises a SiCOH-containing layer formed on the substrate, a silicon oxide (SiOx) layer formed on the SiCOH-containing layer, and a mask layer formed on the silicon oxide layer. A pattern is created in the mask layer. Thereafter, the pattern in the mask layer is transferred to the silicon oxide layer using a first etching process, and then the mask layer is removed. The pattern in the silicon oxide layer is transferred to the SiCOH-containing layer using a second etching process formed from a process composition comprising NF3. Thereafter, the silicon oxide layer is removed using a third etching process.