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

Abstract

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.

Carbon contamination and oxidation of Au surfaces under extreme ultraviolet radiation: An x-ray photoelectron spectroscopy study

“…3), where the corresponding peak intensity fluctuates about the same value without any particular trend (not shown). 2,16 In general, we can conclude that adsorbed hydrocarbons on top of Au were continuously "enriched" with carbon atoms with increasing EUV irradiation time. In fact, sharp increase in intensity of total carbon within the first 60 min of EUV radiation (Fig.…”

“…Figure 6 shows the temporal evolution of the relative peak area intensity for both pure and oxide states of Au. 16,29 As a result of water dissociation, the dissociated fragments, particularly free O atoms, are able to interact and oxidize Au atoms. Considering both these trends, total Au 0 peak intensity was found to be reduced by $4% after 9 h of EUV irradiation.…”

“…Such a combination represents the exact recipe for EUV-induced carbon contamination of the optics. 1,14 However, in-depth understanding of the EUV-induced carbon deposition process on Ru surfaces is hindered by the overlapping of the C 1s and Ru 3d lines in x-ray photoelectron spectroscopy (XPS), 16 which is the most common tool for observing and understanding the surface chemical properties. 9 Typically, mirrors for EUVL systems are prepared by depositing alternating layers of Si and Mo.…”

“…9 Typically, mirrors for EUVL systems are prepared by depositing alternating layers of Si and Mo. 16 Although the accumulation of carbon on Au does not serve as a quantitative indicator for the growth of carbon on Ru surface, it might be useful to understand the physics of hydrocarbons dissociation under EUV irradiation. However, for the sake of better chemical stability of the top Si surface, a thin Ru capping layer has been suggested on top of a Si/Mo MLM.…”

Tracking electron-induced carbon contamination and cleaning of Ru surfaces by Auger electron spectroscopy

“…2 X-ray photoelectron spectroscopy (XPS) is commonly used for estimating carbon contamination in mirrors. 11 However, Auger electron spectroscopy (AES) is better suited for analyzing carbon contamination since it is far more sensitive than XPS in determining elements with low atomic numbers (except hydrogen and helium). 12,13 It should be remembered that similar to XPS signals, there could be overlapping of Auger peaks in multielement samples, as in the Ru/C system.…”