Invited Paper VT-TuM3
Sorption Properties of Non Evaporable Getter Pumps for Selected Hydrocabons and Organic Compounds

Tuesday, October 21, 2008, 8:40 am, Room 205

Non Evaporable Getter (NEG) pumps are very clean, vibration-free, compact UHV pumps able to deliver large pumping speeds for all active gases, including water and hydrogen. Plenty of literature is available describing the sorption characteristics of NEG pumps toward the gases typically present in UHV system, e.g. hydrogen, carbon oxides, water, nitrogen and oxygen. Fewer papers can be found describing the behaviour of NEGs toward hydrocarbons. Most of the experimental data available in the literature are related to pumping of methane or relatively simple hydrocarbons like the lower alkanes. Very few data are available for more complex molecules. On the other hand, pumping of volatile and organic compounds is an issue in a variety of vacuum applications , especially those related to silicon and semiconductor materials processing, wafer in-line inspection, e-beam and Extreme Ultra Violet Lithography (EUVL). In the present study we report the results of specific tests aimed at measuring the pumping speed for some selected organic compounds, namely toluene, decane and methyl methacrylate (MMA). The study shows that NEG pumps can effectively sorb these large organic molecules with high speed and capacity even at room temperature. This opens up the possibility of using NEG pumps in combination with other typical UHV pumps in those systems were organic volatile compounds can be present to improve the ultimate vacuum and mitigate the carbon/oxygen contaminations.