Methods to manufacture integrated circuits are described. Nanocrystalline diamond is used as a hard mask in place of amorphous carbon. Provided is a method of processing a substrate in which nanocrystalline diamond is used as a hard mask, wherein processing methods result in a smooth surface. The method involves two processing parts. Two separate nanocrystalline diamond recipes are combined—the first and second recipes are cycled to achieve a nanocrystalline diamond hard mask having high hardness, high modulus, and a smooth surface. In other embodiments, the first recipe is followed by an inert gas plasma smoothening process and then the first recipe is cycled to achieve a high hardness, a high modulus, and a smooth surface.