Effects of chamber conditions on EUV source efficiency and optical system performance during high-frequency operation

摘要

Buffer gases, used for protection and cleaning of the optical system in the EUV source chamber, as well as the amount of residual vapor and fine mist due to the required high frequency operation for the high-volume manufacture (HVM) may affect the source performance and mitigating system efficiency. Interplay of injected gas flow and evolving Sn plasma/vapor should be studied in conditions closely related to laser produced plasma (LPP) chamber environment. We expanded and enhanced our models implemented in the HEIGHTS package to simulate LPPs in mixture environment of vapor/plasma created from Sn droplet and the background buffer gas (e.g., Ar) at various pressures. Our integrated models allowed self-consistent simulation of EUV produced and EUV induced plasma evolution in the entire chamber. We studied tin plasma evolution in single and dual pulse systems in conditions of Ar residual background gas at 3 and 30 Pa pressure. Details of Ar plasma induced by EUV photons were analyzed to predict conditions near mirror surfaces that could change performance of the surface layers and reflectivity of the collecting optical system. Processes of mixture and two plasmas expansion and cooling from both the pre- and the main pulse were simulated for the first time to predict chamber conditions at the next iteration of target/lasers coupling and interaction.