The development of semiconductor chips is making progress with an astonishing speed, enabling electronic apparatus smaller, higher speed, and higher performance. This dynamic advancement is significantly attributable from the development of photolithography technology. At an early era of integrated circuits (IC) manufacturing lithography technique was introduced with light source of g-line wavelength (436 nm). For further miniaturization of IC the wavelength of light source is getting shorter and shorter, i.e., i-line (365 nm), KrF (248 nm) and ArF (193 nm). Currently ArF immersion is actively investigated as the most advanced technology, and EUV (13.5 nm) is discussed as the next generation lithography. Chemically amplified (CA) resist is mainly employed for the study of the advanced lithography. The CA resist is composed of polymer bearing acid-labile groups and photoacid generator (PAG). Photolytic decomposition of PAG during light exposure generates acids in the CA resist. This acid acts as catalyst to facilitate de-protection reaction of ester group or acetal group of polymer, rendering polymer matrix alkaline-soluble. For achieving desired resist performance such as resolution, depth-of-focus, line edge roughness and etching resistance, the acid-labile polymers have been intensively studied first and developed notably. For further improvement of the CA resist, PAG is the key ingredient. We have developed new oxime sulfonate type PAGs releasing strong acid. A series of oxime sulfonate compounds with various chromophors have been synthesized and the application-relevant properties are presented in this paper.
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-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene (ONPF), 2-
[2,2,3,3,4,4,4-heptafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene (HNBF) and so on. Here the
lithographic property of ONPF in some ArF model formulations was evaluated under 193 nm 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 &ggr;-butyrolactone methacrylate, 2-ethyladamantyl methacrylate and
hydroxyladamantyl methacrylate than in a copolymer of &dgr;-methacryloyloxynorbornane butyrolactone in lactone unit.