23 March 2012 Tin droplets for LPP EUV sources
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Abstract
The tin droplet generator is a key component of EUV LPP sources. Small tin droplets, when combined with a high power laser, form a regenerative target with high CE. A major challenge associated with today's EUV sources is energy stability, which directly correlates with the stability of the fuel delivery system. The LEC droplet dispenser is now in its 5th generation design, with several years of development, including studies of different nozzle types, excitation mechanisms, thermal management approaches and contamination control systems. The dispenser produces droplets in the frequency range required for both metrology and HVM EUV sources. The two relevant instability modes are drop-to-drop jitter and lateral instabilities. The low frequency content of the lateral droplet displacement is compensated by a newly implemented dispenser positioning system. The drop-to-drop jitter, which is studied over 2000 s, equals 11.2% (3σ) of the mean droplet spacing, which makes individual droplet laser triggering necessary. The lateral instabilities, which are mainly relevant in the plane perpendicular to the laser axis, are determined to be in the range of 7.1% (3σ;) of the droplet diameter. The lateral displacements are recorded over 2.2 hrs. The related EUV temporal energy stability (open-loop) is estimated to be 0.35% (3σ) for the worst case scenario, a laser spot size which matches the droplet diameter.
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Bob Rollinger, Bob Rollinger, Luna Bozinova, Luna Bozinova, Nadia Gambino, Nadia Gambino, Reza S. Abhari, Reza S. Abhari, } "Tin droplets for LPP EUV sources", Proc. SPIE 8322, Extreme Ultraviolet (EUV) Lithography III, 83222P (23 March 2012); doi: 10.1117/12.916683; https://doi.org/10.1117/12.916683
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