Efficient specification and characterization of surface roughness for extreme ultraviolet optics

EUV mirrors are cutting-edge optical surfaces. Meeting the roughness specifications over the entire range of relevant spatial frequencies is a challenging process. Recent developments that might help to increase the efficiency of EUV mirror production will be discussed including relaxed roughness specifications using the new Generalized Harvey Shack theory as well as a new approach for roughness measurements during and after manufacturing based on light scattering measurements and analysis. The method provides area covering images of the distribution of high-spatial frequency roughness (HSFR) over entire mirrors. Results will be presented for 660 mm diameter EUV collector mirror substrates.