Tin LPP plasma control in the argon cusp source

Malcolm W. McGeoch

doi:10.1117/12.2222299

18 March 2016 Tin LPP plasma control in the argon cusp source

Malcolm W. McGeoch

Proceedings Volume 9776, Extreme Ultraviolet (EUV) Lithography VII; 97760S (2016) https://doi.org/10.1117/12.2222299
Event: SPIE Advanced Lithography, 2016, San Jose, California, United States

Abstract

The argon cusp plasma has been introduced [1,2] for 500W class tin LPP exhaust control in view of its high power handling, predicted low tin back-scatter from a beam dump, and avoidance of hydrogen usage. The physics of tin ion control by a plasma is first discussed. Experimentally, cusp stability and exhaust disc geometry have previously been proved at full scale [2], the equivalent of 300W-500W usable EUV. Here we verify operation of the plasma barrier that maintains a high argon density next to the collector, for its protection, and a low density in the long path toward the intermediate focus, for efficiency. A pressure differential of 2Pa has been demonstrated in initial work. Other aspects of tin LPP plasma control by the cusp have now been demonstrated using tin ions from a low Hz 130mJ CO₂ laser pulse onto a solid tin surface at the cusp center. Plasma is rejected at the <0.5% level at the collector mirror location using the cusp magnetic field alone. Plasma also is rejected using a low argon density (<1x10¹⁴cm^-3). We have measured the tin ion flow pattern toward the large area annular beam dump. Scaling of the cusp design to match a specified exhaust power is discussed. In view of this work, argon cusp exhaust control appears to be very promising for 500W class tin LPP sources.

Citation Download Citation

Malcolm W. McGeoch "Tin LPP plasma control in the argon cusp source", Proc. SPIE 9776, Extreme Ultraviolet (EUV) Lithography VII, 97760S (18 March 2016); https://doi.org/10.1117/12.2222299

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