[摘要]：The photodegradation at 157 nm of thin films of a series of Teflon AF copolymers has been comprehensively examined using electron spin resonance, NMR, FTIR, and Raman spectroscopies, mass spectrometry and X-ray photoelectron spectroscopy. The mechanism of degradation involves reaction at the dioxole units, and as a consequence the sensitivity to degradation increases across the series Teflon AF 1200, 1600, and 2400. A major volatile product is hexafluoroacetone formed by degradation at the dioxole unit. NMR and volatile product analysis confirm that degradation occurs largely at the dioxole unit leading to an array of new chain-end species. Main-chain and chain-end carbon-centered radicals were identified as arising from abstraction reactions and main-chain cleavage, respectively. In addition to loss of the dioxole units, XPS analysis indicates extensive char formation at the film surface, providing evidence of loss of fluorine atoms which in turn may react with free radical intermediates to form stable products identified by NMR. The implications for design of materials for 157 nm photolithography are discussed.
