Patent ID: 8894767

Claim:
A gas distribution assembly, comprising: an annular body comprising: an annular ring having an inner annular wall positioned at an inner diameter, an outer wall positioned at an outer diameter, an upper surface, and a bottom surface; an upper recess formed into the upper surface; a lip formed radially outward of the inner annular wall; and a seat formed into the inner annular wall; an upper plate positioned in the upper recess, comprising: a disk-shaped body having a plurality of first apertures formed therethrough, wherein the first apertures extend beyond a surface of the body thereby forming raised cylindrical bodies; and a bottom plate positioned on the seat, comprising: a disk-shaped body having a plurality of second apertures formed therethrough which align with the first apertures; and a plurality of third apertures formed between the second apertures and through the bottom plate, the bottom plate sealingly coupled to the upper plate to fluidly isolate the plurality of first and second apertures from the plurality of third apertures.