IR antireflective filtering for EUV multilayer Bragg reflectors

An extreme ultraviolet (EUV) multilayer mirror with an integrated spectral filter for the infrared (IR) range is presented and experimentally evaluated. The design of the antireflective (AR) coating, based on a 10 nm Mo layer and an EUV reflecting and IR transparent B4C/Si multilayer, is significantly simpler than alternatively proposed designs and requires no thick AR layers that may lead to roughness induced EUV performance loss issues. The design has no inherent trade-off between EUV reflectance and IR suppression, maximizing EUV performance. First experimental data shows IR suppression by more than a factor of 150 at a wavelength of 10.6 mm (Fig. 1), with an EUV reflectance of 45%. The AR coating allows high suppression over a large angular acceptance range. Therefore such a mirror could replace conventional multilayer mirrors to suppress undesired spectral components in EUV sources for lithographyAn extreme ultraviolet (EUV) multilayer mirror with an integrated spectral filter for the infrared (IR) range is presented and experimentally evaluated. The design of the antireflective (AR) coating, based on a 10 nm Mo layer and an EUV reflecting and IR transparent B4C/Si multilayer, is significantly simpler than alternatively proposed designs and requires no thick AR layers that may lead to roughness induced EUV performance loss issues. The design has no inherent trade-off between EUV reflectance and IR suppression, maximizing EUV performance. First experimental data shows IR suppression by more than a factor of 150 at a wavelength of 10.6 mm (Fig. 1), with an EUV reflectance of 45%. The AR coating allows high suppression over a large angular acceptance range. Therefore such a mirror could replace conventional multilayer mirrors to suppress undesired spectral components in EUV sources for lithography