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Published online by Cambridge University Press: 22 February 2011
Chemical vapor cleaning (CVC) is an emerging technology which has been used to remove transition metal contamination from wafer surfaces. CVC is a gas phase/surface reaction which does not incorporate any wet steps nor condensation of reagents onto the wafer surface. In previous work, we reported the effective removal of trace iron and copper from native oxide surfaces using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HFAC) and other chelating or coordination compounds. In general, surface metal contaminants form volatile reaction products with these CVC reagents at relatively low temperatures (<300°C). In this paper, we report the extension of that work to include the facile removal of sodium from silicon oxide surfaces. Wafers doped with sodium from aqueous sodium hydroxide can be cleaned in a fully gas phase process at temperatures below 225°C.We will describe our preliminary process results, which have led to a surface sodium concentration reduction of roughly one order of magnitude. Current understanding related to the mechanisms controlling mobile ion removal will also be described.