Blazed XUV Gratings with a Very Low Level of Stray Light

Due to their comparatively high diffraction efficiencies, blazed grazing incidence gratings are frequently preferred in monochromators for the EUV and XUV wavelength ranges (~1 nm to 40 nm). One of the few suitable technologies for their manufacturing is based on an interference lithographic surface patterning. Thus, blazed grating lines with a typically rather large blaze angle are initially generated in photo sensitive resist material on top of the substrate. An adapted subsequent reactive ion etching step allows for a height-scaling during the pattern transfer into the glass substrate. The scaling factor, typically much less than one, simultaneously reduces the blaze angle to the low values required for grazing incidence operation and also reduces the roughness of the photo resist image proportionally. Our continuously optimized process chain led to a new quality in terms of efficiency and homogeneity for the diffractive grating structures as well as to very low stray light. The manufacturing process will be introduced in detail to support a sound evaluation of the potential of this technology. We present and discuss recently achieved results.