Spacer Etching Process

A method for processing a workpiece in a plasma processing apparatus, the plasma processing apparatus comprising a plasma chamber having an interior operable to receive a process gas and a processing chamber having a workpiece support operable to support a workpiece, wherein the workpiece comprises at least one spacer layer and at least one mandrel structure, further wherein the plasma processing apparatus comprises an induction coil disposed about the plasma chamber and a bias electrode disposed in the workpiece support, the method comprising:

• placing the workpiece on the workpiece support in the processing chamber;
• admitting a process gas in the plasma chamber, the process gas comprising a fluorine containing gas and a polymer forming gas;
• providing RF power to the induction coil to generate a first plasma from the process gas to generate a first mixture, the first mixture comprising one or more first species;
• filtering the one or more first species to create a filtered mixture;
• providing RF power to the bias electrode to generate a second plasma in the filtered mixture in the processing chamber to generate a second mixture, the second mixture comprising one or more second species;
• and
• exposing the workpiece to the second mixture to etch at least a portion of the at least one spacer layer of the workpiece and to form a polymer layer on at least a portion of the at least one spacer layer.