In an embodiment, a method of processing a substrate includes introducing a first process gas or a mixture of the first process gas and a second process gas into an etch chamber; exposing the substrate to the first process gas or to the mixture of the first and second process gases, the substrate having halogen residue formed on an exposed surface, the substrate having high aspect ratio features; forming and maintaining a plasma of the first process gas or a plasma of the mixture of the first and second process gases in the etch chamber to remove the residue from the surface by applying a first source power; exposing the substrate to the second process gas; and forming and maintaining a plasma of the second process gas in the etch chamber to remove the residue from the surface by applying a second source power and a bias power.