Reduced contaminant gas injection system and method of using

A treatment system, comprising:

• a process chamber, including a process space;
• a process gas supply system in fluid communication with said process chamber and configured to introduce a flow of a process gas to said process chamber;
• a gas distribution system coupled to said process chamber, said gas distribution system comprises a housing and a gas distribution plate coupled to said housing, the combination of which defines a plenum which receives said flow of said process gas through an entrance to said plenum and distributes said flow of said process gas to a plurality of openings in said gas distribution plate that are in fluid communication with said process space, wherein said housing and said gas distribution plate are formed of a dielectric material, wherein said gas distribution system comprises a process gas diffuser that comprises a divergent passage having an inlet coupled to an exit of said process gas supply system, and an outlet coupled to said plenum and located at said entrance to said plenum of said gas distribution system, said process gas diffuser diffuses the momentum of said flow of said process gas into said plenum, and wherein said outlet of said process gas diffuser comprises a cross-sectional area that is larger than a cross-sectional area of said inlet of said process gas diffuser and smaller than a cross-sectional area of said plenum;
• a holder coupled to said process chamber and configured to support a substrate in said process chamber for exposure to said process gas;
• a vacuum pumping system coupled to said process chamber and configured to evacuate said process chamber;
• and
• an upper electrode coupled to said process chamber and disposed opposite said holder, wherein said upper electrode is coupled to a radio frequency (RF) generator and configured to form plasma in said process space by coupling RF power from said RF generator to said upper electrode and through said gas distribution system to said process gas in said process space, and wherein said gas distribution system is disposed between said upper electrode and said holder.