12 May 2004 In-line monitoring of acid and base contaminants at low ppt levels for 193nm lithography
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Abstract
In this paper, a technique for in-line monitoring of acid and base contamination is described. The technique is applied to purge gas monitoring and the air at the in- and outlet of the active charcoal filters on an ASML PAS5500/1100 193nm scanner is analyzed. Unparalleled lower detection limits (LDL) were obtained, especially for acid detection, where LDLs below 10ppt for SOx were achieved. At the inlet high contamination levels (0.5-3ppb) of NO/HONO and SOx are detected. The filters effectively remove the SOx contamination. The residual SOx contamination could be measured and the average was found to be ~2ppt, corresponding to a filtering efficiency of 99.8%. The filtering efficiency for NO and HONO is significantly lower and was found to be ~98%, which is in agreement with previous reports.1
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Roel Gronheid, Roel Gronheid, Rida Al-Horr, Rida Al-Horr, } "In-line monitoring of acid and base contaminants at low ppt levels for 193nm lithography", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2004); doi: 10.1117/12.599089; https://doi.org/10.1117/12.599089
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