Plasma Enhanced CO₂ Recombination in EUV Drive Lasers

During plasma excitation of CO₂ molecules in drive lasers, up to 60% of the CO₂ decomposes into CO. Typically, Au is used as a catalyst to preferentially recombine CO and O radicals into CO₂. While this can mitigate the decomposition of CO₂, there is still a significant amount of CO present in the system. By adding a secondary, microwave driven plasma to the system at the location of the Au catalyst, O atoms can be stripped away from contaminants created in the laser such as O_x and NO_x compounds. It is hypothesized that by increasing the number of O radicals at the catalytic surface, there will be a higher recombination efficiency, which is directly related to the efficiency of the CO₂ drive laser and overall EUV production efficiency for use in semiconductor manufacturing. To test this hypothesis, a CO₂ laser test platform has been constructed at the Center for Plasma-Material Interactions at the University of Illinois at Urbana-Champaign. This experimental chamber can operate under similar conditions to CO₂ lasers currently used in EUV lithography systems. The system measures chemical species concentrations with the Gencoa OPTIX spectrometer and concentrations of O and N radicals using radical probes. This work serves as a status update on the project with preliminary results of the CO:CO₂ ratio for the following four planned experiments: 1) Cu catalyst with secondary plasma inactive, 2) Cu catalyst with secondary plasma active, 3) Au with secondary plasma inactive, and 4) Au catalyst and secondary plasma active.