Space -- time evolution of low-pressure H2 plasma induced by runaway photoelectrons produced by KrF laser pulse

Extreme Ultraviolet Lithography (EUVL) at 13.5 nm is expected to provide the next generation of ULSI. One of hot EUVL problems is contamination of EUV multilayer optics that compels to search methods of in-situ cleaning. The most promising method is to apply H2 plasma generated over the mirror surface by itself EUV radiation. Therefore investigations of EUV-induced plasma are of great interest for developing such cleaning technology. To model evolution of EUV-induced plasma, the study of H2 plasma induced by photoelectrons extracted from a surface by KrF laser pulse has been done. The experiment was carried out by the space-time resolved probe technique while the analysis was made with using plasma model based on 2D PIC MC code as for electrons and for ions. Comparison of experimental and calculated evolution of probe characteristics provided correct applicability of the probe theory and allowed revealing key mechanisms and parameters which control the evolution of photoelectrons-induced plasma.