Multilayer Zr/Si filters for EUV lithography and for radiation source metrology

The technique for fabrication of thin film filters with high mechanical strength, capable of withstanding the prolonged heat load of 1 W/CM2, has been developed. Freestanding multilayer Zr/Si filters of size 20x150 mm(2) with high transparency of 76% at wavelength lambda = 13 rim were manufactured for EUV lithography tool. We have also developed and fabricated various designs of filters (freestanding or mesh supported) with lower transparency of 40-50% for experiments with intensive EUV sources. The tests of differential pressure withstandability and heat-resistance of filter samples were fulfilled. In order to model the influence on the filter of intensive radiation of the lithography source we have tested Zr/Si film samples by the Joule heating in vacuum at residual pressure of 10(-8) Torr. The testing consisted in continuous heating of Zr/Si films at the electrical power per area unit from 0.5 W/cm(2) to 6 W/CM2 during long period of time (up to 2 months). The influence of the long-term heat load on the transparency of samples at lambda = 13 nm and within wavelength region 0.3 - 2 mu m was investigated.