Substituent positional variations and the lithographic properties of poly(methylstyrene-CO-chloromethylstyrene) resist systems

The lithographic performances of structurally different copolymers of methylstyrene (ortho-, meta- and para-isomers) and chloromethylstyrene (meta- and para-isomers) have been assessed. Linear correlations of the data, based on Charlesby's theory of radiation-induced crosslinking of polymers, demonstrate that sensitivity and contrast are functionally related for this system. Variation of the structure of the chloromethylstyrene component of the copolymers had little effect on the lithographic parameters, but the effect of structural variation of the methylstyrene component was pronounced, the order of increasing sensitivity being ortho < meta < para.