Abstract: A method for plasma treatment of a predetermined portion of a substrate. The impedance of the coil and an established normal plasma is matched with the impedance of a power source, thereby maximizing the efficiency of the transfer of energy from the power source to the coil and producing a resonant plasma. The predetermined portion of the substrate is exposed to the resonant plasma for treatment. Additionally, a method for plasma treatment of a predetermined portion of the outside surface of a filament. The filament is trained through an inlet and exit of a plasma treatment chamber, through an inlet side tubular mask within the chamber, and through an exit side tubular mask within the chamber, each mask being adjustable within the chamber axially of the filament to expose a predetermined segment of the filament to plasma in the chamber while masking the remainder of the filament within the chamber from exposure to plasma.