A method of sputter depositing a substantially circumferentially uniform thin film on a surface of a circular, planar disk-shaped substrate, comprising steps of: (a) providing a cathode sputtering apparatus including: a vacuum chamber; a cathode sputtering source comprising a circularly-shaped sputtering target assembly with a first target having a planar sputtering surface and a circumferentially extending edge; and a circular disk-shaped substrate with a planar surface positioned in spaced opposition to the sputtering surface; and (b) sputter depositing the thin film on the substrate surface while providing the chamber with a substantially uniform flow of at least one process gas around the entirety of the circumferentially extending edge of the sputtering target assembly.