Polymers based on a novel 1,3-perfluorodioxole for use as a soft polymer pellicle in 157nm lithography

A series of copolymers of tetrafluoroethylene and 4-trifluormethoxy-1,3- perfluorodioxole (TFETFMD) were prepared as well as a homopolymer of the dioxole (TEMD) using various free-radical initiators. The copolymers were characterized by ¹⁹F NMR, TGA, DSC and VUV measurements. The transparency at 157nm increased with increasing dioxole content reaching an α (μm ^-1) = 0.76 for an unoptimized homopolymer of the dioxole prepared with a perfluorinated peroxide initiator. Exposure studies of the dioxole homopolymer at 157 nm indicate rapid formation of carbonyl species and therefore an anticipated short lifetime as a potential polymer pellicle for 157 nm lithography.