Methods and apparatus for selectively modifying RF current paths in a plasma processing system

A plasma processing system having a plasma processing chamber, comprising:

• an RF power supply;
• a lower electrode having a conductive portion;
• an insulative component disposed in an RF current path between said RF power supply and said conductive portion;
• and
• a plurality of RF path modifiers disposed between said RF power supply and said conductive portion, each of said plurality of RF path modifiers being disposed at different angular positions relative to a reference angle drawn from a center of said insulative component;
• wherein each of the plurality of RF path modifiers is defined by a same structure so that the plurality of RF path modifiers are arranged symmetrically in a circular arrangement under the conductive portion;
• whereby at least a first one of said plurality of RF path modifiers is electrically connected to said conductive portion and at least a second one of said plurality of said plurality of RF path modifiers is not electrically connected to said conductive portion, wherein said plurality of RF path modifiers are implemented using impedance devices, each of said impedance devices being individually adjustable to define an intentional non-symmetric impedance at different regions around the circular arrangement to compensate for sensed azimuthal non-uniformities in the plasma processing system.