In one embodiment, an apparatus for performing an atomic layer deposition (ALD) process is provided which includes a chamber body containing a substrate support, a lid assembly attached to the chamber body, a remote plasma system (RPS) in fluid communication with the reaction zone, a centralized expanding conduit extending through the lid assembly and expanding radially outwards, a first gas delivery sub-assembly configured to deliver a first process gas, and a second gas delivery sub-assembly configured to deliver a second process gas into the centralized expanding conduit. The first gas delivery sub-assembly contains an annular channel encircling and in fluid communication with the centralized expanding conduit, wherein the annular channel is adapted to deliver the first process gas through a plurality of passageways and nozzles and into the centralized expanding conduit. The second gas delivery sub-assembly contains a gas inlet in fluid communication to the centralized expanding conduit.