Post-modification as a way to improve the lithographic performance of resist materials

Monomer components and composition of a resist polymer have large influence on its lithographic performance. Finding the right components and composition for a resist polymer involves laborious systematic synthesis of different polymers. On the other hand, post-modification offers a convenient way to incorporate desired functional groups into an existing polymer and hence improve its lithographic performance and mechanical properties. Using this method, different groups could be quickly tested and the results could direct the future design of new resist materials. Another advantage of this method is that functional groups which are sensitive to the polymerization condition could also be incorporated. In this paper, we demonstrated the feasibility of using the post-modification method. Through a simple esterification reaction in which the acid groups react with alkyl halides in the presence of 1,8-diazobicyclo[5.4.0]undec-7-ene (DBU) or trialkylamine, three different functional groups were incorporated into the existing IBM Version 2 (V2) methacrylate polymer. The post-modification reaction gave high yield and it is possible to control the percentage of the acid groups modified by the initial feeding ratio of the alkyl halide and the carboxylic acid. Depending on the structures of the added groups, the post-modified resist materials demonstrated improved lithographic performances such as better compatibility towards 0.26 N developer and better etch-resistance than the precursor materials. The synthesis, characterization and lithographic performance of the modified polymers are presented. © 2001 SPIE - The International Society for Optical Engineering.