We report here on a new photometric method for acid quantification in nonaqueous media which has been developed to facilitate quantification for photoacid generators (PAGs) employed in resist compositions for microlithography, but may find application in other fields. The method employs laser excitation of the PAG and is based on the acid-induced bathochromic shift in the absorption spectra of a selected organic dye such as rhodamine B (RB), fluorescein (Fl), coumarin 6 (C6), and 2-[4-(3,4-dimethoxyphenyl)-1,3-butadienyl]benzothiazole (DB). The differences in signal intensity of the protonated form of the sensor are used to evaluate the differences in acid generation efficiencies of the PAGs by relative actinometry. To test this methodology, we have determined the photoacid generation efficiencies of 2-methyl- (1), 2-(2‘-furyl ethylidene)- (2), and 2-(4‘-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (3) in acetonitrile by laser flash photolysis, using direct 308 nm laser excitation for 2 and 3 and 355 nm excitation and various phenothiazine derivatives as sensitizers for 1. The values determined this way for 2 and 3 using the four different dyes coincide fairly well, and the absolute values are in good agreement with those determined independently with an established technique earlier. Under sensitized conditions, the efficiency of acid generation seems to equal the combined quenching efficiencies of the S1 and T1 state of the sensitizers. Experiments in thin polymer films indicate that the same technique could be used to perform in situ acid analysis on coated quartz wafers. This approach has a set of advantages over existing methods and should be applicable to virtually every photoacid generating system by simply selecting the sensor that meets the specific requirements of the PAG under investigation.

The autopolymerization of styrene, styrenic derivatives, and styrene/(meth)acrylate comonomer mixtures in the presence of stable nitroxide free radicals has been shown to be a “living” process. Molecular weight can be controlled by varying the ratio of vinyl monomer to TEMPO and low-polydispersity materials are obtained. Significantly, a definite incubation period is observed during these polymerizations, and the length of this incubation period increases with increasing amounts of TEMPO. The structures of the in situ generated unimolecular initiators which are formed during this incubation period correspond to those expected from a Mayo mechanism for the autopolymerization of styrene. The isolated and purified adducts, 4 and 5, were shown to be effective unimolecular initiators leading to low-polydispersity, controlled molecular weight polymers.

Stable dispersions of nanosilica ranging in size between 8 and 11 nm were coated with tert-butyl acrylate polymer by in situ polymerization of monomer adsorbed on the particles in 2-propanol. The system was developed for use in the encapsulated inorganic resist technology. To achieve a high coating efficiency, silica was first modified with the 3-(trimethoxysilyl)propylmethacrylate (MPS) coupling agent at two different degrees of grafting. The presence of the bound MPS agent and of the polymer at the silica surface was determined by the attenuated total reflection infrared spectroscopy, while the amounts bound were assessed by the thermogravimetric analysis. Under studied conditions, the encapsulation efficiency was governed by the degree of MPS grafting and by the initial concentration of the monomer. Finally, the dissolution rate of these particles in aqueous base, a key parameter in photoresist application, was drastically reduced with increasing amount of grafted tert-butyl acrylate polymer at the silica surface.