Poly4-(1-hydroxyalkyl)styrene based photoresist materials: Design, synthesis and their lithographic performance

Several synthetic approaches are available to make photoresist polymers for deep UV (DUV) lithography. Two approaches were widely used in semiconductor manufacturing: i) direct polymerization of corresponding monomers by (controlled) radical, (living) ionic polymerization ii) thermal or chemical catalyzed deprotection or protection of the macromolecules. The latter approach which is also called polymer modification chemistry (PMC) or polymer analogous chemistry offers several advantageous over the direct polymerization approach. In this presentation, we will provide an overview on the preparation and basic lithographically important characterization of new polymers based on poly(4-(1-hydroxyalkyl)styrene-co-styrene) [Poly(4-HAS-co-S)]. These polymers were synthesized for the first time by PMC and this methodology is an simple alternative for the synthesis of poly(4-HAS-co-S) than conventionally used synthetically challenging free radical or low temperature anionic polymerization of the protected monomer. We have synthesized high and low molecular weight (Mn) polymers with mole fraction of functional group ranging from partial to complete functionalization. Several formulations based on poly(4-HAS-co-S) were developed and tested for negative tone imaging at DUV lithography. Lithographic performance of these polymers at DUV lithography will be compared with their molecular weight and mole fraction of functional groups.