A theoretical study of 30 to 50 angstrom noble gas heavy ion lithography

The feasibility of using heavy noble gas ions to etch 30 to 50 {Angstrom} wide lines in polymethylmethacrylate (PMMA) on a silicon substrate was investigated. The TRIM91 computer code was used to model point sources of neon, argon, xenon, krypton, or uranium ions penetrating a two-dimensional geometry consisting of a 50 {Angstrom} layer of PMMA over a 50 {Angstrom} layer of silicon. For ions with a kinetic energy less than 500 e, the energy deposition is so confined that the proximity effect is virtually nonexistent. These and other considerations indicate that heavy noble gas ions may be ideal for etching angstrom-level features in this geometry.