A method for processing a substrate is provided; wherein the method comprises applying a film of a copolymer composition, comprising a poly(styrene)-b-poly(siloxane) block copolymer component; and, an antioxidant to a surface of the substrate; optionally, baking the film; subjecting the film to a high temperature annealing process under a gaseous atmosphere for a specified period of time; followed by a treatment of the annealed film to remove the poly(styrene) from the annealed film and to convert the poly(siloxane) in the annealed film to SiOx.