Tuner and microwave plasma source

A microwave plasma source comprising:

• a microwave power source;
• a microwave transmission path which transmits a microwave from the microwave power source to a chamber for performing a plasma process on a substrate;
• a tuner provided in the microwave transmission path for matching an impedance of a load in the chamber to a characteristic impedance of the microwave power source;
• and
• an antenna unit for generating a plasma by radiating the microwave into the chamber,
• wherein the tuner includes:
• a body having a tubular outer conductor and a tubular inner conductor coaxially provided in the outer conductor, the body forming a part of the microwave transmission path;
• an annular dielectric slug provided between the outer conductor and the inner conductor, the slug being movable along a longitudinal direction of the inner conductor;
• and
• a drive mechanism for moving the slug,
• wherein the drive mechanism comprises:
• a drive part for applying a driving force;
• a drive transmission part for transmitting the driving force from the drive part to the slug;
• a drive guide part for guiding movement of the slug;
• and
• a holding part for holding the slug at the drive transmission part,
• wherein the drive transmission part, the drive guide part and the holding part are accommodated in the inner conductor.