Role of residual casting solvent in dissolution behavior of poly (3-methyl-4-hydroxystyrene) films

Abstract

Residual solvent present in resist films following spin casting can significantly influence dissolution behavior. We have used radiolabeling to measure solvent remaining in spin cast films after they have undergone various annealing protocols. Films of poly(3-methyl-4-hydroxystyrene) were found to contain a significant fraction of propylene glycol methyl ether acetate (as much as 50 percent by weight) depending on the annealing conditions. 1100 angstrom films contained a higher percentage of residual solvent than 1.2 micrometers films. A diffusion plus evaporation model was used to deduce the diffusion coefficients of residual solvent as a function of film thickness and annealing temperature. We found that diffusion coefficients of residual solvent in 1100 angstrom polymer films are more than two orders of magnitude less than in 1.2 micrometers thick films.