Plasma processing method and apparatus

A plasma processing apparatus comprising:

• a plasma processing chamber having an electrode for placing and retaining plural substrates in turn within said plasma processing chamber;
• a gas feeder for feeding processing gas into said processing chamber;
• a vacuum pump for evacuating gas from said processing chamber via a vacuum valve;
• an RF power supply for supplying RF power to said processing chamber via a matching network;
• a sensor for monitoring an internal pressure of said processing chamber;
• a database unit configured to store criterion values for determining an end of seasoning that is to be performed after wet cleaning;
• a computing unit configured to compare data collected by a collection unit with the criterion values stored in the database unit,
• wherein said computing unit is also configured to determine said end of seasoning when a plurality of conditions, of the following conditions, are satisfied:
• (1) a derivative of an emission intensity ratio (C2/H) between carbon (C2) and hydrogen (H) in a plasma has decreased to a steady value that is used to determine said end of seasoning;
• (2) a peak-to-peak voltage of a RF bias to be fed to the electrode has risen with plasma processing time to a steady value that is used to determine said end of seasoning;
• (3) an opening of said vacuum valve at a time of plasma processing has decreased with plasma processing time to a steady value that is used to determine said end of seasoning;
• (4) a time required to have said internal pressure of said processing chamber reduced to a predetermined vacuum pressure after completion of plasma discharge has decreased with plasma processing time to a steady value that is used to determine said end of seasoning;
• (5) an electrostatic capacitance at a time of matching by a capacitor, which is a component of said matching network, has increased with plasma processing time to a steady value that is used to determine said end of seasoning;
• and
• (6) a time required until ignition of said plasma from feeding of said RF power to said processing chamber via said matching network has decreased with plasma processing time to a steady value that is used to determine said end of seasoning;
• and
• a control unit for controlling an etching apparatus based on an output signal from the computing unit.