Antenna device, radiation method of electromagnetic waves, plasma processing apparatus, and plasma processing method

An antenna device configured to radiate electromagnetic waves, the antenna device comprising:

• a first waveguide;
• a second waveguide;
• a third waveguide;
• a dielectric window;
• a first inner conductor;
• and
• a drive device,
• wherein the second waveguide is connected to an upper wall of the first waveguide and communicates with the first waveguide,
• the dielectric window is in contact with a lower wall of the first waveguide,
• the first waveguide is provided between the dielectric window and the second waveguide, and extends in a direction crossing a tube axis of the second waveguide,
• the first inner conductor penetrates the upper wall, is electrically connected with the upper wall, and extends along a direction of the tube axis from an inside of the first waveguide to an inside of the third waveguide,
• a first end of the first inner conductor is positioned at a center of the third waveguide, in a surface crossing the tube axis,
• the third waveguide is connected to the lower wall on the dielectric window side and communicates with the first waveguide,
• a first opening end of the third waveguide is connected to the dielectric window, and
• the drive device is connected to the first inner conductor, and is configured to drive the first inner conductor in the direction of the tube axis.