Arylonium photoacid generators containing environmentally compatible aryloxyperfluoroalkanesulfonate groups

Photoacid generators (PAGs) producing environmentally benign 2-phenoxytetrafluoroethanesulfonate fluoroorganic sulfonic acids were synthesized. Synthesis and characterization of the new PAGs composed of 2-phenoxytetrafluoroethanesulfonate with diphenyliodonium or triphenylsulfonium units are described. Characteristics of the onium PAGs were evaluated and compared with perfluorobutanesulfonate (PFBS)-based onium PAGs. The newly synthesized compounds efficiently produced sulfonic acid photochemically upon exposure to selected radiation (254 nm, e-beam, and 13.4 nm wavelengths). The sulfonic acid generated from the new PAGs contains far fewer perfluorinated carbon atoms than those found in widely used perfluorooctanesulfonate (PFOS) PAGs and successfully catalyzed deprotection of the acid-labile tert-butoxycarbonyl, methyladamantyl ester, and tert-butyl ester groups present in model positive tone chemically amplified resists (CARs). Their influence on the lithographic performance of chemically amplified resists was investigated using e-beam and extreme ultraviolet (EUV or 13.4 nm) radiation. For the first time, the capability of PFOS-free PAGs for EUV lithographic application in a CAR was demonstrated by comparing resist sensitivity, resolution, and line-edge roughness (LER) with resist formulations containing PFBS-based diphenyliodonium and triphenylsulfonium PAGs. These new PAGs are attractive for lithographic applications as alternatives to the widely used PFOS PAGs because environmental and performance issues require the availability of strong acid PFOS-free photoacid generators.