High Resolution Electron Beam Fabrication Using STEM

Abstract

Recent work on electron beam lithography has centered on improving overlay precision, reducing cost per exposure and perfecting electron resists and processes for the fabrication of silicon integrated circuits. These efforts have produced experimental integrated circuits with higher density than had previously been possible, and have led to cost reductions in manufacturing environments where quick turn-around is essential. High resolution (linewidths < 0.25 /jm) has not been of direct interest although its pursuit has given information about electron scattering effects which influence resist profiles and give rise to proximity effects. Both of these effects can still be important at larger dimensions particularly when linewidth control is of primary importance. In the last two years, new interest in high resolution has arisen because it has become possible to make useful structures with dimensions of a few tens of nanometers. These nanostructures can be handled readily and it is possible to make electrical contact to them. They are of interest in exploring the physical nature of electrical conductivity especially in superconducting structures exhibiting Josephson effects. It should also be possible to use similar techniques to make optical elements for soft x-rays such as zone plates and pinholes.