Ferrite core effects in a 13.56 MHz inductively coupled plasma

We investigate the effects of adding a ferrite core to the rf coil in a cyl indrical inductively coupled plasma, thereby increasing the mutual inductan ce between the rf coil and the plasma at 13.56 MHz. This could reduce resis tive power loss, P-coil(loss) = (IcoillRcoil)-R-2, in the copper coil becau se of lower required rf drive current to ignite and sustain a plasma. The a ir core transformer circuit model of Piejak et al. is modified to account f or the effects of the ferrite core on the rf circuit. Specifically, circuit elements accounting for core power losses and the new primary inductance c reated by the addition of the core are included. The plasma electron densit y created by inductive drive, with and without the core was the same at the same total rf power. Any energy savings in the copper coils are offset by the large core losses at 13.56 MHz due to hysteresis and eddy currents.