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

Abstract

Extreme ultraviolet (EUV) radiation-induced carbon contamination and oxidation of Au surfaces were investigated using x-ray photoelectron spectroscopy (XPS). The Au sample was irradiated by EUV radiation at 13.5 nm for 9 h, while a series of XPS spectra were recorded for monitoring chemical modification during EUV exposure. XPS analysis showed that total carbon contamination (C 1s peak) at the surface was increased by ∼14% after 9 h of EUV exposure, while the C–H component played a dominant role within the first 60 min of EUV irradiation, giving a sharp rise of the corresponding C 1s peak intensity, followed by a slow and linear increase in intensity of the C–C bonds. The later one represents an accumulation of carbon due to the EUV-assisted dissociation of residual hydrocarbons on Au surface. Oxide state of Au was also noticed to be formed during EUV irradiation, and was found to increase continuously before reaching its maximum followed by a progressive decay. The role of water dissociation in the presence of EUV radiation was discussed and correlated with Au oxidation phenomenon.