The photophysical properties of a series of 1,8-naphthalimide photoacid generators were studied by steady state fluorescence and phosphorescence spectroscopy. Emission and excitation anisotropies, triplet quantum yields in polar and nonpolar solvent and photoacid generation were evaluated. The singlet excited state exhibits a low polarity and is strongly deactivated by an efficient intersystem crossing process. In protic solvent, a homolytic singlet cleavage of the N-O bond occurs and leads to the acid production. The existence of a triplet state close to the singlet state was clearly evidenced. The presence of close singlet excited states is supported by fluorescence anisotropy and picosecond laser spectroscopy experiments. Results of DFT calculations well confirm the experimental contentions and yield important information about the cleavage process involved in such compounds.

Polyimide (6FDA-AHHFP) prepared from the polycondensation of fluorinated acid dianhydride (6FDA) and diamine (AHHFP) is soluble in an aqueous base due to the presence of a hydroxyl group in the phenyl group of the diamine segment. Easy acidolysis of the protecting groups of the hydroxyl group was demonstrated with several model compounds of the polyimide that were protected by a number of acyland (alkyloxy)carbonyl groups. The terf-butoxycarbonyl group showed the highest acidolysis rate in these tests. A polyimide (6F-t-BOC) with a terf-butoxycarbonyl (t-BOC) group was thus prepared. On the basis of the results obtained from the model compound, it was expected that 6F-t-BOC would have a high sensitivity because the t-BOC group, as the protecting group, showed the highest acidolysis rate. Although 6F-t-BOC is insoluble in an aqueous base, it is easily converted to an alkaline-soluble polyimide by the acidolysis of this t-BOC group. This implies that polyimide 6F-f-BOC acts as a positive-working photoreactive material in the presence of a photoacid generator. Actually, 6F-f-BOC in the presence of (p-nitrobenzyl)-9,10diethoxyanthracene-2-sulfonate (NBAS) as a photo acid generator showed excellent positive-working characteristics in an aqueous base developer because of the polarity change induced by removing the t-BOC group. The sensitivity and contrast after a postexposure bake at 120 °C for 10 min were 180 mJ/cm2 (365 nm) and 3.4. Resolution higher than 1.0 gm was obtained in the 5-jum-thick film. The kinetics of thermolytically deprotecting the 6F-1-BOC film, when catalyzed by p-toluenesulfonic acid (p-Tos), was studied further in its solid state. The results clearly indicated that the reaction was first order, suggesting it was a typical Aal-1 type reaction requiring no water. The activation energy for the acidolysis was 19.5 kcal/mol. It further became apparent that the diffusion radius of an acid in a 6F-f-BOC film containing p-Tos was ca.14.2 A when heated for 10 min at 80 °C. 6F-t-BOC has 2 mol of t-BOC groups per repeating unit. Examination of their thermolytic acidolysis showed that acidolysis of the first t-BOC group proceeded more slowly than that of the second one in each repeating unit. This was attributed to the fact that an acid could attack the second t-BOC group easier than the first one and was responsible for the steric inhibition of tert-butyl groups around the t-BOC that protected an acid.

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