Multi-gas straight channel showerhead

A showerhead apparatus comprising:

• a first plenum disposed within the showerhead;
• a second plenum disposed within the showerhead;
• a plurality of first gas flow channels formed within the showerhead and in fluid communication with the first plenum;
• a plurality of second gas flow channels formed within the showerhead and in fluid communication with the second plenum, wherein the first plenum is disposed between the second plenum and the first and second gas flow channels;
• a first plurality of gas conduits formed within the showerhead and coupling the first plenum to the first gas flow channels;
• a second plurality of gas conduits formed within the showerhead and coupling the second plenum to the second gas flow channels;
• a plurality of first gas injection holes formed within the showerhead and in fluid communication with the first gas flow channels;
• a plurality of second gas injection holes formed within the showerhead and in fluid communication with the second gas flow channels;
• and
• heat exchanging channels disposed between sets of the first and second gas injection holes, and formed within walls that extend in the direction of the gas injection past the first and second gas injection holes toward a substrate processing volume, wherein the exterior of the walls define mixing channels into which a first gas and a second gas are injected through the first and second gas injection holes to be mixed therein.