Non-ionic photo-acid generators for applications in two-photon lithography

Non-ionic photoacid generators (PAGs) have been designed and synthesized for use in two-photon lithography (TPL). The chromophores in these new PAGs are covalently linked to the photocleavable group by a flexible joint. Their thermal stability, solubility and efficiency to produce acid under both one- and two-photon excitation were characterized. The potential of these PAGs for TPL was tested in two negative-tone resist systems relying on different mechanisms: free-radical/cationic polymerization or a cationically initiated cross-linking reaction. These PAGs needed lower threshold power for polymerization compared to a commercially available photoinitiator, isopropylthioxanthone, and a phot…