Effect of post-etch cleaning on Ru-capped extreme ultraviolet lithography photomask

摘要

Ru-capped extreme ultraviolet lithography photomasks require cleaning after patterning of the absorber layer. In this study, it was confirmed that, during Cl_2 dry etching to remove the absorber layer, RuCU was formed on the Ru capping layer surface, and the surface roughness thereby deteriorated. Therefore, the changes in RuCl_3 formation and surface roughness with various cleaning processes were investigated. Among the treatments used, i.e., sulfuric peroxide mixture, an ammonia peroxide mixture or ozonated water (DIO_3), DIO_3 exhibited the most effective Cl removal efficiency and surface roughness recovery. DIO_3 treatment successfully reduced the Cl-terminated Ru surface to its original state and decreased the surface roughness to the pre-Cl_2-etched Ru value.