Probing temporal evolution of extreme ultraviolet assisted contamination on Ru mirror by x-ray photoelectron spectroscopy

摘要

Extreme ultraviolet (EUV) radiation mediated carbon contamination and oxidation of the Ru mirror surface, and the corresponding impact on reflectivity were studied. In particular, time-dependent systematic decrease in EUV reflectivity with a 13.5 nm wavelength of light in high vacuum atmosphere was recorded and correlated with the change in chemical composition on the Ru surface as derived from in situ x-ray photoelectron spectroscopy (XPS). The contamination on Ru surface is caused by residual impurities of the test chamber. The recorded XPS spectra show a sudden increase in carbon concentration in the first 1 h followed by a slow but linear growth in the presence of EUV radiation. Further analyses show a slight increase in Ru oxide, whereas the concentration of water molecules decreases continuously. Moreover, the carbon monoxide level at the surface was stabilized after initial increase in concentration for an hour. The impact of water molecules and the accumulation of carbon atoms on the Ru surface are discussed in details.