LASER PHOTOLYTIC STUDIES OF SENSITIZERS FOR NEGATIVE PHOTORESISTS - 2,7-DIAZIDOFLUORENE IN POLY(METHYL METHACRYLATE) FILMS

The time evolution of the transient absorption spectra of 2,7-diazidof luorene (DAF) (N-3-R-N-3) under excimer laser irradiation has been inv estigated in poly(methyl methacrylate) (PMMA) films and in inert cyclo hexane solution and compared with the results for 4,4'-diazido-3,3'-di methoxybiphenyl (DADMB), which has a similar biphenyl skeleton to DAF. The results from a DAF-cyclohexane solution containing diethylamine i ndicated that, in addition to the triplet azido nitrene (:N-R-N-3) whi ch was the main intermediate, didehydroazepine derivatives were genera ted. The formation of these intermediates in solution and in PMMA film s Was completed within the duration of the laser pulse. The reaction o f these intermediates in-solution was completed within 10 ms and in PM MA films within 100 s, while the reaction related to the azido nitrene of DADMB in PMMA films continued up to 1200 s. The results for 1% w/w DAF-doped PMMA films irradiated with a high fluence indicated that th e azido nitrene and the dinitrene (:N-R-N:) underwent dimerization and /or further polymerization, suggesting that DAF molecules form aggrega tes even in dilute PMMA films (1% w/w).:The difference in the miscibil ity of DAF and DADMB in PMMA affected the photoreaction behaviour of t hese diazido compounds in polymer films.