In this paper, we report the achievement of high‐resolution exposures in the organic negative resist SAL 601‐ER7 (Shipley Co. designation), and also in an optimized inorganic As–S:Ag negative resist system, suitable for in situ processing. Sensitivity curves are presented for the organic material, showing the particularly high sensitivity and contrast of this material at exposure voltages ranging from 10 to 40 keV. High aspect ratio (15:1) patterns were formed with the organic resist but mechanical stability was lacking in these structures. A discussion of optimization of material composition is also given for an inorganic resist system based on As–S chalcogenide. The ultimate resolution attained during this study was 50‐nm lines on a 100‐nm pitch for the organic material and 35‐nm lines on a 70‐nm pitch for the inorganic resist system.