Mechanistic simuilarities in the photochemistry of two classes of photocacid generators: a laser flash photolytic study

摘要

An understanding of the fundamental photochemistry of photoacid generators (PAGs) is essential for the design of new PAGs for use in materials for 193 nm and DUV lithography. The photochemical behavior of some N-oxysuccinimidoarylsulfonate(1) and 1,2-di(arylsulfonyl)hydrazie (2) PAGs has been studied by means of nanosecond laser flash photolysis ( lambda _(exc) chemical bounds 266 nm) and steady-state photolysis ( lambda _(exc) chemical bounds 254 nm) in order to investigate the mechanism of reaction, particularly, that of photoacid generation. Upon photoexcitation, the formation of arylsulfonyl radicals has been detected by laser flash photolysis for both of htrese classes of PAGs. The arylsulfonyl radicals can undergo desulfonylation thereby generating SO_2 and aryl radicals; which in O_2-saturated solution are converted into arylperoxy radicals. The arylsulfonyl radical generates acid via reaction with O_2 to yield a peroxysulfonyl radical which subsequently reacts with a hydrogen atom donor to yield a peroxysulfonic acid. The suflfonic acids detected in product studies are presumably the stable decomposition products of this first formed peroxysulfonic acid. Photoacid generation quantum yields upon laser excitation were found to range from 0.04-0.05 for 1 and 0.05-0.1 for 2. Photoacid generation quan tum yields upon lamp irradiation were considerable higher, approx 0.4. Based on this ork, these materials may offer potential as PAGs for 193 nm and DUV lithography.