Scalable and uniformity controllable diffusion plasma source

A method of treating a substrate with plasma, comprising:

• disposing a substrate in a plasma processing system having a power source having a positive terminal and a negative terminal, the positive terminal coupled to ground;
• disposing a DC (direct current) hollow cathode plasma source including a plurality of DC hollow cathodes within said plasma processing system, each DC hollow cathode coupled to the negative terminal of the power source through a respective adjustable conductive element, each DC hollow cathode independently controlled via the respective adjustable conductive element, each DC hollow cathode defining a plasma discharge space bounded by cathode walls opposing one another about a central axis that intersects a cathode outlet at one end of said hollow cathode allowing fluid communication with an interior space of said plasma processing system;
• disposing a grid between said cathode outlet of said plurality of DC hollow cathodes and said substrate;
• electrically coupling said grid to electrical ground;
• generating plasma in said plasma discharge space by ion-induced secondary electron emission of energetic electrons that move along a trajectory substantially normal to said central axis;
• and
• diffusing lower energy electrons along a trajectory substantially parallel to said central axis across a first region of said interior space between said cathode outlet and said grid, through said grid, and into a second region of said interior space in fluid contact with said substrate.

A method of treating a substrate with plasma, comprising:

• disposing a substrate in a plasma processing system having a power source having a positive terminal and a negative terminal, the positive terminal coupled to ground;
• disposing a radio frequency (RF) hollow cathode plasma source including a plurality of RF hollow cathodes within said plasma processing system, each RF hollow cathode coupled to the negative terminal of the power source through a respective adjustable conductive element, each RF hollow cathode independently controlled via the respective adjustable conductive element, each RF hollow cathode defining a plasma discharge space bounded by cathode walls opposing one another about a central axis that intersects a cathode outlet at one end of said hollow cathode allowing fluid communication with an interior space of said plasma processing system;
• disposing a grid between said cathode outlet of said plurality of RF hollow cathodes and said substrate;
• electrically coupling said grid to electrical ground;
• generating plasma in said plasma discharge space by ion-induced secondary electron emission of energetic electrons that move along a trajectory substantially normal to said central axis;
• and
• diffusing lower energy electrons along a trajectory substantially parallel to said central axis across a first region of said interior space between said cathode outlet and said grid, through said grid, and into a second region of said interior space in fluid contact with said substrate.