High‐sensitivity, high‐resolution, high‐thermal‐resistant negative electron x‐ray resist

A novel negative‐working electron/x‐ray resist with high sensitivity, high resolution, and good dry etch resistance was obtained by the free radical copolymerization of an unsaturated methacrylate and a hydroxy alkyl methacrylate. Depending on the copolymer ratio, sensitivity of at least 0.2 μC/cm2 was achieved with 10 keV electrons in most cases with polymers with a ?w well below 100 000. Resolution of 1.0 μm line and space was obtained from a 0.95‐μm‐thick resist by either direct e‐beam writing or by exposure to soft x‐rays through a mask. The sensitivity to 7 A tungsten M lines was 9 mJ/cm2 and the contrast was ∠1.3. An aspect ratio of ∠2 was obtained with isolated submicron lines 7000 A thick. The resist had good resistance to both chemical and dry etching. The plasma etch resistance was at least twice that of PMMA.