Top magnets for decreased non-uniformity in PVD

A magnet assembly comprising:

• one or more magnets;
• a base plate having a top surface and a bottom surface defining a thickness of the base plate;
• a housing on the base plate, the housing having a bottom ring with a top surface and a bottom surface defining a thickness of the bottom ring, an inner diameter with an inner peripheral face and an outer diameter with an outer peripheral face, the bottom ring having a plurality of openings extending through the thickness of the bottom ring, and a housing annular wall extending a height from the top surface of the bottom ring, the housing annular wall having an inner diameter with an inner peripheral face and an outer diameter with an outer peripheral face defining a wall thickness;
• a top plate on the housing, the top plate having a top surface and a bottom surface defining a thickness of the top plate, and an inner diameter with an inner peripheral face and an outer diameter with an outer diameter face, the top plate having a plurality of openings extending through the thickness of the top plate, the plurality of openings aligned with the plurality of openings in the bottom ring of the housing;
• and
• a cover plate having a cover plate top wall and a cover plate annular wall, the cover plate top wall having a top surface and a bottom surface defining a thickness of the cover plate top wall, the cover plate annular wall having an inner diameter with an inner diameter face and an outer diameter with an outer diameter face defining a wall thickness, the cover plate annular wall extending a height from the bottom surface of the cover plate top wall and having an outer diameter less than the inner diameter of the housing annular wall.