Deep X-ray lithography at ELETTRA using a central beam-stop to enhance adhesion

In the deep X-ray lithography process adhesion of resist structures on metallic coated substrate is strongly correlated with the spectral distribution of the radiation. At ELETTRA the bending magnet radiation spectrum extends up to 20 keV which can severely increase the secondary radiation process from the metal coated resist substrate, especially when the deep lithography process is used for mask replication involving lower resist and absorber thicknesses. To reduce the proportion of high energy photons in the radiation spectrum the central part of the beam is blocked by a beam-stop acting as a low energy band-pass filter. The results of the first expositions at ELETTRA using different size beam-stops are presented and discussed.