Development of an EUVL collector with infrared radiation suppression

Laser-produced plasma (LPP) sources for extreme ultraviolet lithography (EUVL) systems utilize CO 2 lasers operating with wavelength 10.6μm. Since multilayer-coated optics have high reflectivity for this infrared radiation (IR), a significant and detrimental amount of IR is passed through the EUVL system. One method to remove the IR from the system is to utilize a binary diffraction grating. When this grating is applied directly to the surface of the primary collector optic of the source, the majority of the IR is diverted outside the radius of the exit aperture at the intermediate focus (IF). This paper will report details on the performance of a full size (410mm diameter) Demonstration Collector utilizing IR rejection (IRR) technology with the capability to produce over 125X suppression of IR, equaling the performance of a IR spectral filter. Additional details will be reported on the technology development and use of a glassy smoothing layer to enable high EUV performance, a weighted average multilayer reflectance of 50.9% for unpolarized EUV radiation.