Silicon planar refractive optics for coherent x-ray sources: metrology and manufacturing approaches

The X-ray planar compound refractive lenses (CRLs) made of monocrystalline silicon by a lithography and plasma deep Si etching (Bosch process) were considered. The CRL is a planar structure of biconcave parabolic refractive surfaces etched into silicon wafers down to 70 μm. The geometrical parameters of the parabolic lens structures were measured by different SEM-based methods and compared with CAD data. The influence of the manufacturing errors on the CRLs optical properties was discussed. The approaches for the improvement of the lens manufacturing techniques were proposed.