Idriss Blakey - Mechanism of 157 nm Photodegradation of Poly[4,5-difluoro-2,2- bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Teflon AF)

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  Publication Details (including relevant citation   information):

  Blakey, I.; George, G. A.; Hill, D. J. T.; Liu, H.; Rasoul, F.;   Rintoul, L.; Zimmerman, P.; Whittaker, A. K., Macromolecules   (Washington, DC, United States) 2007, 40 (25), 8954-8961.

  DOI: 10.1021/ma071549m


  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.

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