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7 April 2017 Modeling and measurement of hydrogen radical densities of in situ plasma-based Sn cleaning source
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Extreme ultraviolet (EUV) lithography sources expel Sn debris. This debris deposits on the collector optic used to focus the EUV light, lowering its reflectivity and EUV throughput to the wafer. Consequently, the collector must be cleaned, causing source downtime. To solve this, a hydrogen plasma source was developed to clean the collector in situ by using the collector as an antenna to create a hydrogen plasma and create H radicals, which etch Sn as SnH4. This technique has been shown to remove Sn from a 300-mm-diameter stainless steel dummy collector. The H radical density is of key importance in Sn etching. The effects of power, pressure, and flow on radical density are explored. A catalytic probe has been used to measure radical density, and a zero-dimensional model is used to provide the fundamental science behind radical creation and predict radical densities. Model predictions and experimental measurements are in good agreement. The trends observed in radical density, contrasted with measured Sn removal rates, show that radical density is not the limiting factor in this etching system; other factors, such as SnH4 redeposition and energetic ion bombardment, must be more fully understood in order to predict removal rates.
© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE) 1932-5150/2017/$25.00 © 2017 SPIE
Daniel T. Elg, Gianluca A. Panici, Jason A. Peck, Shailendra N. Srivastava, and David N. N. Ruzic "Modeling and measurement of hydrogen radical densities of in situ plasma-based Sn cleaning source," Journal of Micro/Nanolithography, MEMS, and MOEMS 16(2), 023501 (7 April 2017).
Received: 2 December 2016; Accepted: 9 March 2017; Published: 7 April 2017


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