Methods for processing a dielectric film to improve its uniformity of thickness and refractive index are disclosed. The dielectric film is deposited using conventional approaches, such as chemical vapor deposition (CVD) or spin coating. The workpiece, with the applied dielectric film is then processed to improve the uniformity of the thickness. This processing may comprise implanting a thinning species to the thicker portions of the dielectric film to reduce the thickness of these portions. The thinning species may be silicon or another suitable species. This processing may alternatively or additionally include implanting a thickening species to the thinner portions of the dielectric film to increase their thickness. The thickening species may be helium or another suitable species. This approach may reduce the variation in thickness by 50% or more.