Plasma processing apparatus

A plasma processing apparatus comprising:

• a chamber;
• a first gas supply configured to supply a processing gas into the chamber;
• an exhaust device configured to exhaust a gas within the chamber;
• a substrate support including a lower electrode electrically floating from a ground potential and provided within the chamber;
• an upper electrode provided above the substrate support;
• a first power supply electrically connected to the upper electrode and configured to generate high frequency power or to periodically generate pulses of DC voltage;
• a ring electrode provided around the substrate support so as to surround the substrate support and connected to ground;
• a second gas supply that supplies a purge gas such that the purge gas flows upwardly through a gap between the ring electrode and the substrate support;
• a discharge electrode disposed along the ring electrode;
• a second power supply electrically connected to the discharge electrode and configured to cause an electrical discharge between the discharge electrode and the ring electrode;
• and
• a dielectric portion provided between the ring electrode and the discharge electrode,
• wherein the exhaust device is configured to exhaust the gas within the chamber via an exhaust port provided on a sidewall of the chamber and disposed above the ring electrode,
• the second gas supply supplies the purge gas through a gas introduction port provided on a wall of the chamber below the substrate support, and
• the discharge electrode and the dielectric portion are provided within a concave portion defined by the ring electrode.