24 May 2004 Contaminant dry-down rates in photolithography purge gases
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Adsorption and desorption rates of a 6-component hydrocarbon mixture and SO2 have been studied on the surfaces of Ultra High Purity (UHP) components under the presence of parts-per-billion (ppb) contaminant levels. The dry-down rates are monitored to sub parts-per-trillion (ppt) levels. In the hydrocarbon test, stainless steel components are confirmed to be more effective than Teflon during dry-down. Dry-down rates for hydrocarbons on stainless steel (SS) surfaces depend on the molecular weight of the contaminant; heavier molecules take longer to dry-down. The dry-down study for SO2 revealed that it will desorb from Teflon surfaces quicker than it will desorb from stainless steel. The result of UHP valves tested for outgassing indicates that Extreme Clean Dry Air (XCDA) was able to remove hydrocarbons to lower levels and cleanup faster than with a N2 purge.
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Allan Tram, Allan Tram, Russell J. Holmes, Russell J. Holmes, Jeffrey J. Spiegelman, Jeffrey J. Spiegelman, Daniel Alvarez, Daniel Alvarez, "Contaminant dry-down rates in photolithography purge gases", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); doi: 10.1117/12.534296; https://doi.org/10.1117/12.534296

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