Method and apparatus for insulating a high power RF electrode through which plasma discharge gases are injected into a processing chamber

A processing system for processing a substrate with a plasma comprises a processing chamber defining a process space including a support structure for supporting a substrate within the process space. A gas inlet in the chamber introduces a process gas into the chamber and a showerhead positioned within the chamber disperses process gas from the inlet. A supply of electrical energy biases the showerhead to form a plasma with process gas dispersed by the showerhead. First and second electrical insulator elements are positioned between the showerhead and the processing chamber, and are operable to electrically insulate the showerhead from the processing chamber. The first and second electrical insulator elements each have a passage therethrough for passing a process gas from the gas inlet through the insulator element and the respective passages of the insulator elements are laterally spaced from each other. A channel is formed in one of the elements and extends between the spaced passages to couple the passages together and form a complete passage through the first and second insulator elements for passing a process gas to the showerhead.