Fluorine-free Photoacid Generators for 193 nm Lithography Based on Non-Sulfonate Organic Superacids

We are introducing a new family of fluorine-free photoacid generators (PACs) for use in 193 nm lithography. These PAGs are based on percyano-substituted cyclopentadienide anions and do not contain sulfonate groups. PACs with these weakly coordinating anions generate photoacids of a similar strength as perfluroalkylsulfonic acids. Triphenylsulfonium pentacyanocyclopentadienide (TPS CN5) can be synthesized from inexpensive precursors, is stable in the presence of strong acids, has a low optical density at 193 nm and is well soluble in typical resist solvents. The performance of model resists formulated with TPS CN5 approaches that of commercially offered photoresists for the 32 nm node.