Study on radiation chemistry of fluorinated polymers for EUV resist

The fluorination of a chemically amplified resist is an effective method for use in EUV lithography. However, it has been suggested that the fluorination of the base polymer of the chemically amplified resist induces the electron scavenging reaction by the base polymer and reduces the acid yield. In this study, we clarified the formation of transient species and the acid yields of fluorinated polymers after exposure to the ionizing radiations. The acid yields of fluorinated polymers with hydroxyl groups were lower than that of poly(4-hydroxystyrene) (PHS). The lower acid generation efficiency in fluorinated polymers was due to not only the reaction between fluorinated polymers and electrons but also the lower deprotonation efficiency of the radical cation of the fluorinated polymer.