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 20×150 mm2 with high transparency of 76% at wavelength λ = 13 nm 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/cm2 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 λ = 13 nm and within wavelength region 0.3 - 2 μm was investigated.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.