Monte Carlo study of surface and line-width roughness of resist film surfaces during dissolution Original Research Article

Molecular simulations are becoming necessary at the length scales of nanolithography, since material models used for the bulk are no longer applicable. At the same time film thickness of materials used throughout the lithographic steps in modern device fabrication reduce down to the order of tens of polymer chain radii of gyration, resulting in great proportions of surface and line-edge roughness over the total film thickness and width, respectively. The dissolution mechanism of these materials is still lacking a final description in the level of full microscopic details. The dissolution of a general positive tone chemically amplified resist film is simulated, using the critical ionization model [P.C. Tsiartas, L.W. Flanagin, C.L. Henderson, W.D. Hinsberg, I.C. Sanchez, R.T. Bonnecaze, C. G. Willson, Macromolecules 30 (1997) 4656]. The polymer film was considered as consisting of polymer chains comprising random walks or self-avoiding random walks on a square two-dimensional lattice. The site-sharing concept is introduced and analyzed in order to produce the desired polymerization length per chain in a highly populated lattice with and without excluded volume effects. The model is used to investigate the variation of surface and line-width roughness in terms of excluded volume effects and polymerization length for high exposure doses.