Semi-classical energy loss in EUV plasma generated tin ion collisions with a hydrogen buffer gas

The stopping of tin ions originating from a laser produced plasma (LPP) in a hydrogen
gas is of considerable interest for ASML’s modern extreme ultra violet (EUV) lithography
machines. Near the LPP, EUV collector mirrors are placed which have shown to deteriorate
from exposure to energetic tin ions Snq+. A promising solution is to add a hydrogen buffer
gas in LPP chamber. However the interaction and stopping power of Snq+ with H2 is still not
fully understood. This makes it difficult to determine the minimum necessary H2 pressure
for total stopping. In this research a semi-classical collision model called Groningen Ion
Stopping (GIonS) has been improved with the adoption of DFT interaction potentials for
Sn1+, Sn2+. Stopping results have shown close resemblance with what has been found by
Abramenko et al. in 2018. Additionally some heavily debated characteristic features in the
Abramenko data, such as a dip in Sn2+ stopping cross-sections from initial energies of 4
keV upwards, can be further brought into question. This project shows that the description
of stopping through a collision model with DFT based potentials is a valid and promising
method to further study tin ion – hydrogen interactions.