Properties and Lithographic Capability of Sulfonium Salts with Aromatic Cyclic Ketone Group for ArF Chemically Amplified Resist

Abstract

We evaluated dialkylsulfonium salts with an aromatic cyclic ketone structure (a 1-indanone, 1-tetralone, or 4-chromanone unit) as a photoacid generator for ArF chemically amplified resists. The thermal stability of the salts was affected by alkyl subsitituents. Sulfonium salts with two methyl groups or a pentamethylene group exhibited a decomposition temperature of more than 200 °C. The absorption coefficients at 193 nm for the new PAGs were 1/3 to 1/4 that of the conventional triphenylsulfonium salt. The photosensitivity of sulfonium salt with the 1-oxo-2-indanyl group with an ArF laser was two times that of a phenacyl sulfonium salt with an aromatic linear ketone structure. We also analyzed the photodecomposed compounds produced by irradiation with an ArF excimer laser. A positive resist using a dimethyl(1-oxo-2-indanyl)sulfonium salt achieved a 130 nm line-and space pattern.