Tuner, microwave plasma source and impedance matching method

A tuner, to which a microwave is supplied from a microwave power source, of transmitting the microwave to a planar antenna which radiates the microwave and matching an impedance of a plasma load with a characteristic impedance of the microwave power source in a plasma processing apparatus in which a plasma process is performed by generating plasma within a chamber with the microwave, the tuner comprising:

• a microwave transmission path, having a coaxial structure, configured to transmit the supplied microwave to the planar antenna;
• at least two slugs made of a dielectric material and configured to be moved along the microwave transmission path;
• a driving unit configured to move the at least two slugs along the microwave transmission path;
• and
• a control unit configured to perform impedance matching by controlling positions of the at least two slugs such that the at least two slugs are located at a matching position where a reflection coefficient is small, and configured to control, based on a state of the plasma, a matching track through which the at least two slugs reach the matching position.