Monitoring acidic and basic molecular contamination in leading edge lithography and metrology applications: quantitative comparison of solid state and impinger-based sampling methods

Sarah Riddle Vogt; Cristian Landoni

doi:10.1117/12.846364

1 April 2010 Monitoring acidic and basic molecular contamination in leading edge lithography and metrology applications: quantitative comparison of solid state and impinger-based sampling methods

Sarah Riddle Vogt, Cristian Landoni

Author Affiliations +

Proceedings Volume 7638, Metrology, Inspection, and Process Control for Microlithography XXIV; 763825 (2010) https://doi.org/10.1117/12.846364
Event: SPIE Advanced Lithography, 2010, San Jose, California, United States

Abstract

Assessing molecular contamination (MC) at part-per-billion (ppbV) or part-per-trillion volume (pptV) levels in cleanroom air and purge gas lines is essential to protect lithography and metrology tools optics and components. Current lithography and metrology tool manufacturer's specifications require testing of some contaminants down to single digit pptV levels. Ideally this analysis would be performed with an on-line analyzer (capable of providing almost instant results): the best analyzers currently available are only capable of providing 100 pptV detection. Liquid impinger sampling has been the dominant sample collection method for sub ppbV acidic and basic MC analysis. Impinger sampling suffers from some inherent problems that can dramatically reduce the collection efficiency such as analyte solubility and evaporative losses. An innovative solid-state trapping technology has been recently developed by SAES Pure Gas along with the CollectTorr sampling system. NIST traceable gas phase standards have been used to compare the collection efficiency of the traditional impinger technology to that of the solid state trapping method. Results varied greatly for the different acid gases with sulfur dioxide showing comparable collection efficiencies while hydrofluoric acid and hydrochloric acid showed much lower recoveries in the impingers than the solid-state traps. Ammonia collection efficiencies were slightly higher for the solid state traps and were improved in the impingers when an acidified solution was used as the collection media. The use of solid-state traps, besides being much simpler from both the handling and logistical stand point, eliminates the analyte solubility and evaporation problems frequently seen with the impinger sampling.

Citation Download Citation

Sarah Riddle Vogt and Cristian Landoni "Monitoring acidic and basic molecular contamination in leading edge lithography and metrology applications: quantitative comparison of solid state and impinger-based sampling methods", Proc. SPIE 7638, Metrology, Inspection, and Process Control for Microlithography XXIV, 763825 (1 April 2010); https://doi.org/10.1117/12.846364

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