Patent ID: 7132621

Claim:
A method of forming a plasma comprising: flowing a gas into a multi-mode processing cavity; and igniting the plasma by subjecting the gas in the cavity to electromagnetic radiation having a frequency less than about 333 GHz in the presence of at least one passive plasma catalyst comprising a material that is at least electrically semi-conductive, wherein the plasma catalyst comprises at least one electrically conductive component and at least one additive in a ratio, the method further comprising sustaining the plasma, wherein the sustaining comprises: directing additional electromagnetic radiation into the cavity; and allowing the catalyst to be consumed by the plasma such that the plasma contains the at least one additive, and wherein the ratio differs for differing portions of the catalyst, and wherein the allowing comprises allowing the differing portions of the catalyst to be consumed by the plasma at differing times such that the plasma contains a varying ratio of the electrically conductive component to the at least one additive.