Exhaust assembly for a plasma processing system

A plasma processing system configured to process a substrate with plasma, comprising:

• a plasma processing chamber having a chamber wall enclosing a process space and configured to facilitate the formation of a processing plasma in the process space;
• a substrate holder coupled to the plasma processing chamber and configured to support said substrate;
• a plasma generation system coupled to the plasma processing chamber and configured to form said processing plasma from a process gas in the process space adjacent said substrate;
• a vacuum pumping system coupled to the plasma processing chamber and configured to evacuate said process gas from the process space;
• an exhaust assembly coupled to the plasma processing chamber around said substrate holder and separating said process space from a pumping space coupled to the vacuum pumping system;
• an electrical power source coupled to the exhaust assembly and configured to form a secondary plasma in order to alter said processing plasma;
• the exhaust assembly comprising:
• a first annular exhaust plate surrounding said substrate holder and extending between the substrate holder and the chamber wall to separate the process space from the said pumping space;
• electrical insulation members coupled to the first exhaust plate and configured to insulate the first exhaust plate from the substrate holder and the chamber wall;
• and
• a second annular exhaust plate surrounding the substrate holder and extending between the substrate holder and the chamber wall between the first annular exhaust plate and said pumping space to form a secondary plasma space between the first exhaust plate and the second exhaust plate;
• the first exhaust plate having a plurality of openings therethrough to allow passage of said process gas therethrough from the processing chamber to said second exhaust plate and the second exhaust plate having a plurality of openings therethrough to allow passage of said process gas therethrough from the secondary plasma space to said pumping space;
• wherein the first exhaust plate is coupled to the electrical power source and the second exhaust plate is coupled to electrical ground;
• wherein the secondary plasma is being formed in the secondary plasma volume between said first exhaust plate and the second exhaust plate;
• a controller programmed to control said plasma processing system to perform the following steps:
• disposing a substrate on the substrate holder in the plasma processing chamber;
• forming a processing plasma in a process space above and adjacent the substrate disposed on the substrate holder in the plasma processing chamber using the plasma generation system coupled to said plasma processing chamber;
• coupling electrical power to the exhaust assembly within said plasma processing chamber that substantially surrounds said substrate holder and separates said process space from a pumping space coupled to the vacuum pumping system, thereby forming a secondary plasma in order to alter said processing plasma to thereby expose said substrate to said altered processing plasma;
• said first exhaust plate having a plurality of openings to allow passage of process gas therethrough;
• said second exhaust plate being parallel with said first exhaust plate and below said first exhaust plate, said second exhaust plate having a plurality of openings to allow passage of process gas therethrough;
• and
• said controller is programmed to control the plasma processing system to couple electrical power between the first exhaust plate and a ground electrode that is coupled to an electrical ground, and forming the secondary plasma between the first exhaust plate and the ground electrode.