Multilayer coating and tests of a 10x extreme ultraviolet lithographc camera

Abstract

A new set of mirrors for the SANDIA I OX microstepper has been fabricated. The optics have been tested by optical profilometry, atomic force microscopy, EUV reflectometry and EUV scattering. These measurements allow one to predict the performance of the camera. Mo/Si multilayer coatings with the required thickness profile were produced by DC magnetron sputtering using shadow masks in front of the rotating substrates. The failure errors of the new mirrors (0.6 nm) are considerably smaller than those obtained previously, while mid-spatial frequency roughness still needs improvement. This roughness reduces mostly the throughput of the system; i. e. most of the scattered light occurs outside the field of the camera and there is only a small reduction of contrast or resolution