Transparent photoacid generator (ALS) for ArF excimer laser lithography and chemically amplified resist

A novel photoacid generator, ALS (alkylsulfonium salt; cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethane- sulfonate) for ArF excimer laser ((lambda) equals193 nm) lithography and a single-layer resist have been developed. ALS shows high transparency at 193 nm and photoacid generating capability on irradiation by ArF excimer laser. A novel methacrylate terpolymer, poly(tricyclo[5.2.1.02,6]decanylmethacrylate-co-2- tetrahydropyranylmethacrylate-co-methacrylic acid), is synthesized as a base resin. The resist, consisting of ALS and the polymer, shows chemical amplification and good resolution. A 0.2-micrometers line and space negative-tone image is observed at 15 mJ/cm2 dose using an ArF excimer laser.