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.

中文翻译：

---

聚[4,5-二氟-2,2-双（三氟甲基）-1,3-二氧杂环戊烯-共-四氟乙烯]（Teflon AF）的157 nm光降解机理

使用电子自旋共振，NMR，FTIR和拉曼光谱，质谱和X射线光电子能谱，已全面检查了一系列Teflon AF共聚物薄膜在157 nm处的光降解。降解机理涉及二恶唑单元处的反应，因此，整个系列的Teflon AF 1200、1600和2400对降解的敏感性增加。主要的挥发性产物是在二恶唑单元处降解形成的六氟丙酮。NMR和挥发性产物分析证实降解主要发生在二恶唑单元上，从而导致一系列新的链端物质。主链和链端碳中心自由基分别被确定为源自抽象反应和主链裂解。除了损失二恶唑单元之外，XPS分析表明，在薄膜表面形成了大量炭，这提供了氟原子损失的证据，而氟原子又可能与自由基中间体发生反应，形成了由NMR鉴定的稳定产物。讨论了157 nm光刻材料设计的意义。