Sputtering chamber having auxiliary backside magnet to improve etch uniformity and magnetron producing sustained self sputtering of ruthenium and tantalum

A magnet system for a plasma sputter chamber, comprising:

• a source magnetron having
• an outer magnet assembly comprising magnets of a first magnetic polarity that is oriented along a first direction and
• an inner magnet assembly comprising at least one magnet of an opposed second magnetic polarity that is oriented opposite the first direction, surrounded by the outer magnet assembly, and separated therefrom by a closed first gap,
• wherein a first ratio of the magnetic strength of the outer magnet assembly to the magnetic strength of the inner magnet assembly of the source magnetron is at least three, and
• wherein the source magnetron is rotated in back of a target assembly about the central axis;
• and
• an auxiliary magnetron disposed away and spaced from an outer side of the source magnetron in a second direction from the inner pole toward the central axis, overlying the central axis, and having an outer magnet assembly comprising magnets of the first magnetic polarity that is oriented along the first direction, surrounding an inner magnet assembly comprising at least one magnet of the second magnetic polarity that is oriented opposite the first direction, and separated therefrom by a closed second gap, wherein the inner and outer magnet assemblies of the auxiliary magnetron have substantially equal magnetic strengths.