Improvements of Nanostructure Patterning in X-Ray Mask Making

Abstract

In order to evaluate the resolution limits and to achieve a high resolution X-ray lithography under proximity condition, masks compatible with Karl Suss XRS200 stepper have been fabricated with a conventional electron beam lithography at 50 keV energy and a reactive ion etching (RIE) technique for the pattern transfer. It was found that with a relative thin (300 nm) tungsten absorber 50 nm linewidth and high density gratings of period down to 120 nm can be fabricated without proximity correction. Experimental results with gratings of different linewidths and different periods are analyzed to clarify the process parameter influences on the dose correction. In addition, the fabricated masks were tested by proximity replication with Karl Suss stepper at a gap of 5 µ m using synchrotron radiation. Finally the replication results were discussed in terms of the resolution limit as a function of proximity gap.