Metrology in the Soft X-Ray Range - from EUV to the Water Window

Metrology in the soft X-ray range has various applications ranging from instrumentation for solar astronomy to plasma experiments and EUV Lithography. The Physikalisch-Technische Bundesanstalt (PTB) with its laboratory at the electron storage ring BESSY II is a centre of soft X-ray radiometry and supports national and European research and development by carrying out high-accuracy at-wavelength measurements. The absolute detection efficiency of entire detection systems, diodes or cameras can be traced to SI units with a typical relative uncertainty of 0.5 % to 1 % using a cryogenic electrical substitution radiometer. For reflectometry on multilayer mirrors (MLMs) PTB operates a large reflectometer accommodating samples of up to 550 mm in diameter and 50 kg in weight, allowing sample alignment in 6 degrees of freedom. The relative measurement uncertainty for the spectral reflectance is typically in the range of 0.15 % and the long-term reproducibility in the range of 0.10 %. To investigate roughness, scatterometry is employed where scattered light around the specular beam is mapped using a calibrated CCD.