Control of Presentation of Functional Ultraviolet Absorbers to the Surface of Photoresist Polymers Using Low Surface Energy Polymers

Bilayer polymer thin films, that form through the surface segregation of a surface-active component, provide the ability to tailor interfacial properties and are relevant to many technological applications, including photolithography. For example, polymers with fluorine-containing end groups will selectively accumulate at the polymer–air interface when the second polymer is not fluorinated, but what happens when both polymers in a bilayer film are fluorinated? To test this, we prepared polymers via reversible addition–fragmentation chain transfer (RAFT) polymerization, which were then end group modified with a fluorine-containing small molecule or by chain extension with a fluorinated monomer to form a short fluorine-containing block. These partially fluorinated polymers were then blended with an extreme ultraviolet (EUV) photoresist that had a degree of in-chain fluorination, and thin films of the blends were prepared. To probe multilayer formation and assess the competition of the end group modified, fluoro-block, and in-chain fluorinated groups for the polymer–air interface, the films were characterized using contact angle measurements and static time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results reveal important insights into the effect of fluoro-block length on directing self-segregation of the polymeric additive. The effect of the addition of the low surface energy polymer on the lithographic performance of the photoresist was confirmed using electron beam lithography.