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Three metal-catalyzed vinyl addition copolymers derived from partially fluorinated norbornenes and tricyclononenes have been synthesized and evaluated for use in formulating photoresists for 157 nm lithography imaging. The transparency of these polymers at 157 nm, as measured by variable angle spectroscopic ellipsometry (VASE), is greatly improved over their nonfluorinated counterparts. The results of preliminary lithographic evaluations of resists formulated from these polymers alone and with the addition of several new fluorinated dissolution inhibitors are presented. Images as small as 70 nm have been printed in some formulations.

The photochromic couple dihydroazulene/vinylheptafulvene (DHA/VHF) is an established system for molecular switching. The photoinduced ring opening of the thermally stable dihydroazulene proceeds in the picosecond time regime with subsequent rapid relaxation to the electronic ground state. So far it was not possible to reverse the reaction photochemically. It was always found that the back reaction proceeds thermally on a longer time scale. In the case of the cyanophenyl-DHA derivative utilized in the present study, this is accounted to s-cis/s-trans isomerization of the primarily formed s-cis VHF. Since this particular isomerization takes much longer than nanoseconds, we now successfully applied a second visible femtosecond pulse subsequent to the initial UV pulse (25 ps delay) achieving ring closure of the primarily formed s-cis VHF. The now bidirectional photoswitching was monitored by the changes in the cw spectrum. As a result, the DHA/VHF system is found to be a multifold switchable system by itself: it is both a very fast photoreversible switch and a photochemical/thermal switch with a thermal lock mode.

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