Abstract: Some embodiments provide a magnetron sputtering apparatus including a vacuum chamber within which a controlled environment may be established, a target comprising one or more sputterable materials, wherein the target includes a racetrack-shaped sputtering zone that extends longitudinally along a longitudinal axis and comprises a straightaway area sandwiched between a first turnaround area and a second turnaround area, a gas distribution system that supplies a first gas mixture to the first turnaround area and/or the second turnaround area and supplies a second gas mixture to the straightaway area, wherein the first gas mixture reduces a sputtering rate relative to the second gas mixture. In some cases, the first gas mixture includes inert gas having a first atomic weight and the second gas mixture includes inert gas having a second atomic weight, wherein the second atomic weight is heavier than the first atomic weight.