Wafer pedestal with a purge ring

摘要

A wafer pedestal with a purge ring that circumscribes a peripheral edge of the wafer pedestal. The purge ring contains plurality of passages that are located proximate the peripheral edge of said wafer pedestal such that purge gas is directed towards the peripheral edge. Additionally, the purge ring cooperates with an edge ring assembly that circumscribes the purge ring. The purge ring and the edge ring assembly allow a dual-purge flow pattern to be established, which significantly reduces the accumulation of undesirable deposits upon the wafer pedestal.