A method for controlling chemical dry etching to improve smoothness of an etched surface is disclosed. Ions are implanted into a surface to form a volatilizable compound at a temperature low enough to avoid, reduce, or eliminate formation of three-dimensional structures of the volatilizable compound that might create the roughness at an etched surface of the volatilizable compound. The ions are applied in a sufficient energy to penetrate to a predetermined depth of material that is to be removed from the surface in an etching cycle, and in a sufficient dosage to achieve full formation of the volatilizable compound. The surface of the volatilizable compound is exposed to a gas composition for a time duration sufficient to completely etch the volatilizable compound.