The direct comparison of the emission characteristics of an extreme ultraviolet (EUV) light between the CO2 and the Nd:YAG laser-produced plasmas (LPP) with a solid tin target is reported. In the case of the Nd:YAG LPP, the conversion efficiency (C.E.) peaked at a laser intensity of about 5×1010W∕cm2 and decreased at higher laser intensity. In the case of the CO2 LPP, the C.E. monotonically increased up to 2×1010W∕cm2, where the C.E. is comparable to the maximum C.E. of the Nd:YAG LPP. The spectral efficiency of the Nd:YAG LPP within the 2% bandwidth around 13.5 nm decreased with laser intensity. The corresponding spectral efficiency of the CO2 LPP was almost constant. This observation indicates the potential of the CO2 laser-produced LPP as the EUV light source for the EUV lithographic systems.

We propose a CO2 laser-produced plasma as the extreme ultraviolet (EUV) light source for a future optical lithography system. The EUV radiation around 13.5 nm was generated by focusing the laser beam from a transversely-excited atmospheric CO2 laser (4 J, 50 ns full width at half-maximum (FWHM)) on a Xe gas target and a Xe cryogenic target. The EUV energy was measured by a Flying Circus II detecting system, and an output energy of more than 3 mJ/pulse and an conversion efficiency of more than 0.1% per 2π sr at 13.5 nm were obtained. These values are comparable to those of Nd:YAG laser-produced plasma, indicating the potential scalability of the EUV light source using a CO2 laser produced plasma.

We propose CO 2 laser-produced plasma as the extreme ultraviolet (EUV) light source for future optical lithography. The laser beam from a transversely-excited atmospheric (TEA) CO 2 laser (4 J, 50 ns FWHM) was focused on a Xe gas target, a Xe cryogenic target and a nano-structured tin-based target to generate EUV radiation around 13.5 nm. The EUV pulse of about 100 ns in FWHM was measured 50 ns after the CO 2 laser irradiation. The EUV spectra were measured by an X-ray CCD camera with a transmission grating spectrograph (TGS). A characteristic EUV spectrum was observed from CO 2 laser produced Xe plasma. The EUV energy was measured by a Flying Circus II detecting system and an output energy of 3 mJ/pulse and a conversion efficiency of 0.2 % per 2π sr at 13.5 nm (2% B.W.) were obtained with Xe targets. These values are comparable to those of YAG laser-produced Xe plasma, indicating the potential scalability of the EUV light source using a CO 2 laser produced plasma.

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