Methods and apparatus for controlling photoresist line width roughness

A method for controlling line width roughness of a photoresist layer disposed on a substrate comprising:

• after a photoresist layer has been patterned on a substrate to form openings, supplying a gas mixture through a waveguide in an uninterrupted flow path into a processing chamber having the substrate disposed therein;
• applying a microwave power from a microwave power generator through a dielectric window to the processing chamber to generate an electric field in the waveguide in the processing chamber, the waveguide having a first end closed by the dielectric window formed as a lid of the processing chamber and a second end facing the substrate, the window exposed to the substrate through the waveguide;
• applying DC or AC power to one or more coils or magnets disposed around an outer circumference of the processing chamber to generate the magnetic field in the waveguide;
• forming a plasma in the gas mixture by the interaction of the magnetic field and the electric field with uninterrupted path in the waveguide, wherein the gas mixture is supplied into the first end of waveguide, the gas mixture flowing through the waveguide toward the substrate to the patterned photoresist layer;
• and
• trimming an edge profile of the patterned photoresist layer using the plasma formed in the processing chamber.