Emission characteristics of Nd:YAG and CO2 laser-produced tin plasmas for extreme ultraviolet lithography source development
Laser-produced plasmas (LPPs) are being considered as a light source for the next generation of extreme ultraviolet (EUV) lithography. In this thesis work, the differences in emission characteristics between Nd:YAG and CO2 LPPs is explored. The purpose for this work is to determine potential advantages of using CO2 LPPs versus Nd:YAG LPPs for EUV source development. The characteristics investigated include both particulate and radiative emission features. To accomplish this goal a suite of diagnostic tools was employed. Particulate analysis revealed that the quantity of debris ejected from the Nd:YAG LPP was considerably higher than that of the CO 2 LPP. It was also noted that the debris emission, both atomic and ionic, was forward-centric for the Nd:YAG LPP; however, in the case of the CO2 LPP, more lateral expansion was observed. The plasma densities were estimated using Interferometry and optical emission spectroscopy (OES) studies and it was found that the density of the Nd:YAG LPP was considerably higher than the CO2 LPP throughout the lifetime of the plasma. This difference in density results in more efficient laser-plasma coupling in the case of the CO2 LPP as well as significantly higher production of neutral tin species in the Nd:YAG LPP.
Hassanein, Purdue University.
Theoretical physics|Plasma physics
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