Externally excited torroidal plasma source with a gas distribution plate

A plasma reactor for processing a workpiece, said plasma reactor comprising:

• a vacuum enclosure, including a wall, defining a vacuum chamber, said vacuum chamber having a main chamber portion on one side of said wall and a plenum on another side of said wall, said plenum communicating with said chamber portion through at least one opening in said wall;
• a workpiece support within said main chamber portion and facing said wall;
• a gas distribution plate coupled to said wall, said wall separating said main chamber portion from the plenum, facing said workpiece support and coupled to a reactive process gas supply for injecting reactive process gases directly into a process region adjacent said workpiece support;
• a gas injection port at said plenum coupled to a diluent gas supply for injecting diluent gases into said plenum;
• and
• a first coil antenna adapted to accept RF power, inductively coupled to the interior of said plenum, and capable of maintaining a plasma in a reentrant path through the plenum and across the process region.