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Exposure of collector mirrors facing the hot, dense pinch plasma in plasma-based EUV light sources to debris (fast ions,
neutrals, off-band radiation, droplets) remains one of the highest critical issues of source component lifetime and
commercial feasibility of nanolithography at 13.5-nm. Typical radiators used at 13.5-nm include Xe and Sn. Fast
particles emerging from the pinch region of the lamp are known to induce serious damage to nearby collector mirrors.
Candidate collector configurations include either multi-layer mirrors (MLM) or single-layer mirrors (SLM) used at
grazing incidence.
Studies at Argonne have focused on understanding the underlying mechanisms that hinder collector mirror performance
at 13.5-nm under fast Sn or Xe exposure. This is possible by a new state-of-the-art in-situ EUV reflectometry system
that measures real time relative EUV reflectivity (15-degree incidence and 13.5-nm) variation during fast particle
exposure. Intense EUV light and off-band radiation is also known to contribute to mirror damage. For example offband
radiation can couple to the mirror and induce heating affecting the mirror's surface properties. In addition, intense
EUV light can partially photo-ionize background gas (e.g., Ar or He) used for mitigation in the source device. This can
lead to local weakly ionized plasma creating a sheath and accelerating charged gas particles to the mirror surface and
inducing sputtering.
In this paper we study several aspects of debris and radiation-induced damage to candidate EUVL source collector
optics materials. The first study concerns the use of IMD simulations to study the effect of surface roughness on EUV
reflectivity. The second studies the effect of fast particles on MLM reflectivity at 13.5-nm. And lastly the third studies
the effect of multiple energetic sources with thermal Sn on 13.5-nm reflectivity. These studies focus on conditions that
simulate the EUVL source environment in a controlled way.
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