Properties of ion debris emitted from laser-produced mass-limited tin plasmas for extreme ultraviolet light source applications

Properties of ion debris emitted from laser-produced mass-limited tin plasmas have been experimentally investigated for an application to extreme ultraviolet (EUV) lithography. Simple scaling laws to design the mass-limited target, which is a key technique to minimize contamination of the first EUV collection mirror, is discussed. The measured energy spectrum of the tin ions is consistent with a prediction by the isothermal expansion model. The average charge state of the tin ions is evaluated to be +5 at 180mm away from the plasma, and higher-energy ions have higher charge state. It was found that not only EUV emission but also ion energy spectra are sensitively affected by the target mass limitation.

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