Sulfonium salts of alicyclic group functionalized semifluorinated alkyl ether sulfonates as photoacid generators

We describe new sulfonium salts incorporating semifluorinated sulfonate anions and their successful application as photoacid generators (PAGs) intended to solve the environmental problems caused by perfluorooctyl sulfonate (PFOS). By utilizing simple and unique chemistries based on 5-iodooctafluoro-3-oxapentanesulfonyl fluoride, a series of alicyclic-group functionalized octafluoro-3-oxapentane-sulfonate anions were prepared in high purity and high yield. Triphenylsulfonium (TPS) salts of norbornyl and γ-butyrolactone groups functionalized octafluoro-3-oxapentanesulfonates were extensively studied. They have excellent thermal stability and good solubility in various polar solvents. Their optical and thermal properties were thoroughly investigated. Angle resolved X-ray photoelectron spectroscopy (XPS) analysis confirmed that the new TPS salts are uniformly distributed in polymer films, whereas TPS PFOS is heavily segregated to a polymer film surface. Lithographic performance of the new salts together with ...