Magnetron for low pressure, full face erosion

A plasma system for sputtering a surface of a target, said system comprising:

• a vacuum chamber;
• a magnetron source which holds the target in the chamber during processing, said magnetron source producing a magnetic field next to the surface of the target;
• and
• a platform within the chamber which supports a substrate during processing,
• wherein said magnetron source comprises:
• a first magnet assembly located behind a location which the target will occupy during processing and arranged to generate a magnetic field over an area in front of the target that is confined primarily to an inner region of that area, said inner region of the area in front of the target being surrounded by an outer region;
• a second magnet assembly also located behind the location which the target will occupy during processing and arranged to generate a magnetic field over an area in front of the target that is confined primarily to the outer region of the surface of the target;
• and
• a lift mechanism which during use causes relative movement between the first magnet assembly and at least a portion of the second magnet assembly so as to control the relative strength of the magnetic field in the outer region relative to the magnetic field in the inner region.