New laboratory EUV reflectometer for large optics using a laser plasma source

The quality assurance for the production of optical components for Extreme Ultra Violet Lithography (EUVL) strongly requires at-wavelength metrology. Presently, at-wavelength characterizations of mirrors and masks are done using the synchrotron radiation of electron storage rings, e.g. BESSY II. For the production process of EUV optics, however, the immediate access to metrology tools is necessary and the availability of laboratory devices is mandatory. Within the last few years a stand alone laboratory EUV reflectometer for large samples has been developed. It consists of a laser produced plasma (LPP) radiation source, a monochromat or and a large goniometer system. The manipulation system of the reflectometer can handle samples with diameters of up to 500 mm, thicknesses of up to 200 mm and weights of up to 30 kg. The wavelength can be varied from 10 nm to 16 nm. The spot size on the sample surface is about 2 mm. The angle of incidence can be varied from 3° to 60°. In this paper, we describe the laboratory reflectometer in detail and discuss the achieved performance. First measurements of 4" mirrors are presented and discussed in comparison to the results obtained at the PTB soft X-ray radiometry beamline at BESSY II.