Process parameters for submicron electron beam lithography of NPR.

NPR (Novolac Positive Resist), a high resolution (0.25microns) positive electron beam resist, is a blend of a cresol novolac and a polymeric dissolution inhibitor, poly(2-methyl-1-pentene sulfone) (PMPS) which undergoes spontaneous depolymerization during electron irradiation. Stringent control of processing parameters is necessary to obtain resist sensitivity, contrast and linewidth control. The study of the chemistry of NPR has been discussed previously. In this paper we report on the role of processing variables on pattern quality and identify the conditions necessary for submicron resolution.