Influence of the development process on ultimate resolution electron beam lithography, using ultrathin hydrogen silsesquioxane resist layers

The influence of the development process on the ultimate resolution of electron beam lithography using ultrathin HSQ layers was studied. Different developers, of different types and strengths, were used to develop lines exposed at a variety of doses. Optimum exposures could be found for lines of widths between 7 and 12nm, at a pitch of 20nm. Lines smaller than 5nm could not be fabricated using any of these developers. Changing the development time had no influence on this result. Width versus dose curves are presented for all three developers and a 60s development time. A scaling is presented to enable an easy calculation of the exposure latitude for each linewidth. Using 100keV electron beam lithography, we achieved 6nm isolated features in a 10nm thick HSQ layer on a silicon substrate. We also showed that dense structures (5nm wide at a pitch of 20nm) could be obtained using a 1:5 developer solution of Microposit 351:H2O.