We have developed and evaluated new chemically amplified molecular resists based on fullerene derivatives with an excellent solubility in a standard alkali developer for extreme ultraviolet (EUV) lithography. We controlled the electron acceptability of fullerene derivatives and applied photo-acid generators (PAGs) with a high electron acceptability through ionization by EUV irradiation. As a result, sensitivities of positive-tone molecular resists based on fullerene derivatives were markedly improved, and we succeeded in obtaining good resolution, by applying an organic underlayer substrate without pattern collapse. Delineations of 45 nm half pitch (hp) and line width roughness (LWR) of 5.7 nm were achieved at an exposure dose of 12.5 mJ/cm2 on the organic underlayer.

A novel method using trialkylphosphines is reported for the facile purification of [60]fullerene containing C 60 O. When tri-n-butylphosphine and tri-n-octylphosphine were added to unrefined C 60 (ca. 97% purity) in 1,2,4-trimethylbenzene, C 60 O was readily reduced to give high-purity C 60 (>99% purity). The best results were obtained for a high concentration (>1.0 wt %) of unrefined fullerene treated with tri-n-octylphosphine at room temperature. This method is simple and fast in comparison with conventional alumina chromatography, and thus, it is well-suited to industrial-scale separation.

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