Non-ionic photoacid generators for chemically amplified resists: evaluation results on the application-relevant properties

Recently we have developed and reported some novel non-ionic photoacid generators (PAGs) which generate a strong acid (perfluorobutanesulfonic acid) by light irradiation and is applicable to chemically amplified ArF photoresist, such as 2-[2,2,3,3,4,4,5,5-octafluoro-l-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene (ONPF), 2[2,2,3,3,4,4,4-heptafluoro-l-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene (HNBF) and so on. Here the lithographic property of ONPF in some ArF model formulations was evaluated under 193 run dry and immersion exposure comparing one of the most typical ionic PAGs, triphenylsulfonium perfluorobutanesulfonate (TPSPB), on lithographic application-relevant properties, e.g. exposure latitude, line edge roughness (LER) and so on, by top-down view SEM observation. 80 nm line and space (L/S) patterning was successfully conducted. Additionally we investigated the striation issue with ONPF when the matrix polymer of resist was changed. It was revealed that ONPF showed better coating property in a copolymer of gamma-butyrolactone methacrylate, 2-ethyladamantyl methacrylate and hydroxyladamantyl methacrylate than in a copolymer of delta-methacryloyloxynorbomane butyrolactone in lactone unit.