Efficient 13.5nm extreme ultraviolet emission from Sn plasma irradiated by a long CO2 laser pulse

The effect of pulse duration on in-band (2% bandwidth) conversion efficiency (CE) from a CO2 laser to 13.5nm extreme ultraviolet (EUV) light was investigated for Sn plasma. It was found that high in-band CE, 2.6%, is consistently obtained using a CO2 laser with pulse durations from 25to110ns. Employing a long pulse, for example, 110ns, in a CO2 laser system used in an EUV lithography source could make the system significantly more efficient, simpler, and cheaper as compared to that using a short pulse of 25ns or shorter.

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