US Patent 8742669 Passive power distribution for multiple electrode inductive plasma source

Systems, methods, and Apparatus for controlling the spatial distribution of a plasma in a processing chamber are disclosed. An exemplary system includes a primary inductor disposed to excite the plasma when power is actively applied to the primary inductor; at least one secondary inductor located in proximity to the primary inductor such that substantially all current that passes through the secondary inductor results from mutual inductance through the plasma with the primary inductor. In addition, at least one terminating element is coupled to the at least one secondary inductor, the at least one terminating element affecting the current through the at least one secondary inductor so as to affect the spatial distribution of the plasma.