A deposition system includes a magnetron sputter deposition source that includes a backing frame that includes a window and a closed loop around the window. The backing frame includes inside surfaces towards the window, one or more sputtering targets mounted on inside surfaces of the backing frame, and one or more magnets mounted on outside surfaces of the backing frame. The one or more sputtering targets include sputtering surfaces that define internal walls of the window. The one or more magnets can produce a magnetic field near the one or more sputtering surfaces. A substrate includes a deposition surface oriented towards the window in the backing frame. The deposition surface receives sputtering material(s) from the one or more sputtering targets.