Organic gases cause carbon depositions on the multi-layer mirrors by Extreme Ultra Violet (EUV) light irradiations in EUV lithography tool. The dependences on organic gas species, organic gas pressure and EUV light intensity in the carbon deposition were researched in order to understand this reaction. EUV light was irradiated on a (Si/Mo) multilayer mirror sample injecting organic gas like buthane, buthanol, methyl propionate, hexane, perfluoro octane, decane, decanol, methyl nonanoate, diethyl benzene, dimethyl phthalate and hexadecane. X-ray photoelectron spectroscopy measurements revealed that organic gases with heavier molecule weight or higher boiling temperature caused faster carbon deposition rates. Carbon deposition rates increased linearly with organic gas pressures. Dependence on EUV light intensity was estimated from comparisons between an EUV light profile and carbon distributions on irradiated samples. Carbon deposition rates increased rapidly, but became saturated at higher EUV light intensities. Three chemical reactions, an adsorption, a desorption and a carbon deposition by EUV light irradiation, were taken into account to explain the behavior of the carbon deposition. Electron irradiation on a mirror sample revealed that photoelectrons emitting from the mirror surface played an important role in carbon deposition.

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Determination of bonding structure of Si, Ge, and N incorporated amorphous carbon films by near-edge x-ray absorption fine structure and ultraviolet Raman spectroscopy

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A new contamination evaluation system that can irradiate high-flux extreme ultraviolet (EUV) and measure, in situ, the reflectivity of multilayer mirrors for EUV lithography (EUVL) projection optics was constructed to develop a contamination inhibition mechanism at the NewSUBARU synchrotron radiation (SR) facility. The vacuum chambers of the systems are all metal sealed. All automatic stages in the system are driven by motors set outside the chambers. The optimum pressure of the chamber was 2 ×10-7 Pa, two orders of magnitude higher than that in the system reported last year. The partial pressure of the hydrocarbon components was also two orders of magnitude smaller than that in the previously reported system. In the first experiment using the system, the lifetime of Si-capped Mo/Si multilayer mirrors was evaluated as a function of water vapor pressure. The system can also be used to measure and map X-ray absorption near-edge structure (XANES) spectra in the irradiated area, which is very important for the in situ evaluation of the contamination mechanism.