where it is ignited into a plasma 122 by a current applied to the showerhead 108 by a power source 120 in one embodiment the power source 120 may comprise an rf power source fig2 is a schematic cross sectional view of an etching apparatus 200 according to one embodiment of the invention the apparatus 200 comprises a processing chamber 202 having a substrate 204 disposed therein the substrate 204 may be disposed on a susceptor 206 that is movable between a raised and a lowered position the substrate 204 and the susceptor 206 may sit opposite to a showerhead 208 within the processing chamber 202 a vacuum pump 210 may draw a vacuum within the processing chamber 202 the vacuum pump 210 may be disposed under the susceptor 206 processing gas may be provided to the processing chamber 202 from a gas source 212 to a plenum 214 above the showerhead 208 the processing gas may flow through gas passages 216 into the processing area 218 the showerhead 208 may be biased with a current from a power source 230 the current may flow to the showerhead 208 whenever the switch 228 is turned on in one embodiment the power source 230 may comprise an rf power source in another embodiment the showerhead 208 may be open or at floating potential when the substrate 206 is biased an rf current applied to the substrate 206 will travel to ground.