A new class of negative-tone resist materials has been developed for electron beam and extreme ultraviolet lithography. The resist is based on heterometallic rings. From initial electron beam lithography studies, the resist performance demonstrated a resolution of 40-nm pitch but at the expense of a low sensitivity. To improve the sensitivity, we incorporated HgCl₂ and HgI₂ into the resist molecular design. This dramatically improved the resist sensitivity while maintaining high resolution. This improvement was demonstrated using electron beam and extreme ultraviolet lithography.