Christopher G. Morgan and Ronald Vane*, XEI Scientific, Inc., 1755 E. Bayshore Blvd., Redwood City, CA
Presentation at the EUV Lithography Workshop, June 2011, Maui, Hawaii
Carbon contamination on extreme ultraviolet (EUV) optics reduces their reflectivity. Further studies of the effect cleaning multilayer blanks capped with either silicon or ruthenium by the Evactron system are presented. Room air and argon/oxygen mixtures are used as the cleaning gas. EUV reflectivity of the blanks and surface roughness are measured post cleaning to determine if the cleaning process is both effective and not harmful. Preliminary data shows that the oxygen mixtures are very effective at removing PMMA resist from a silicon wafer. Additionally the use of hydrogen gas with the Evactron De-Contaminator is explored. Optical emission spectra of the plasma show that hydrogen radicals are created by the Evactron system. Cleaning effectiveness can be determined by using quartz crystal microbalances. The hydrogen atoms remove carbon contamination with maximum cleaning occurring at 100 mTorr chamber pressure. Rates around 1 nm per minute have been measured when the Evactron system is 15 cm from the quartz crystal microbalance.