Abstract
ArF excimer laser (λ=193.4nm) lithography is a promising technology for manufacturing 1-Gbit DRAMs (<0.2μm design rule). A new positive chemically amplified resist for ArF wavelength which consists of a novel photoacid generator (PAG) and a methacrylate terpolymer with tricyclodecanyl (TCD) group, has been developed. The PAG shows good thermal stability up to 151°C, high transparency, and high acid generation efficiency for an ArF excimer laser exposure. The photochemical reaction of PAG occurs mainly in the lowest triplet state T1, and it is concluded to the bond dissociation of S- (2-oxocyclohexyl) group. Then the cyclohexanone anion reacts with its counter anion, and generates trifluoromethanesulfonic acid. A new base polymer with TCD groups demonstrated high transparency (69.3%/μm), high thermal stability up to 141°C, a good dry-etching resistance, and high solubility for an aqueous base (tetramethylammanium hydroxide) developer. A pattern with 0.20 μm lines and spaces has been resolved using an ArF excimer laser lens (NA=0.55).
