High resolution e-beam lithography for X-ray mask making

The electron energy of, e.g., 50 keV has advantages over less electron energy for X-ray mask substrates because the influence of the proximity effect is reduced. However, also in the case of writing with high energy electrons on thin membranes, the proximity effect cannot be neglected. Starting with one experimentally defined exposure dose the calculation of the proximity compensation dose is made by the Monte Carlo simulation and the proximity function. High resolution structures down to 50 nm were written on X-ray mask substrates as well as on bulk silicon wafer and compared with CAD data. The pattern placement accuracy of the e-beam system was investigated for the resolution of 50 nm over the stepfield of 3 x 3 square meter on an X-ray mask. (IMT)