Fluorinated Components in High-Volume Lithography Materials Are Transformed to Generate PFASs under Oxidizing and Reducing Conditions

Fluorinated polymers are essential for lithographic patterning during electronics fabrication, and a variety of per- and polyfluoroalkyl substances (PFASs) of unknown sources are frequently measured in wastewater from electronics fabrication facilities (fabs). We tested the hypothesis that the fluorinated polymers contained in top antireflective coatings (TARCs) can be transformed under oxidizing or reducing conditions to form PFASs measured in fab wastewater. Three TARCs were characterized using combustion ion chromatography and 19F and 13C nuclear magnetic resonance (NMR) spectroscopy to quantify total fluorine and characterize structural features of the fluorinated components. Transformation experiments were conducted under oxidizing and reducing conditions, and products were identified by means of 19F NMR, high-resolution mass spectrometry, and ion chromatography. Under oxidizing conditions, fluorinated components transformed to primarily produce perfluoroalkylcarboxylic acids (PFCAs) when the structure contained nonfluorinated carbon atoms. Under reducing conditions, more highly fluorinated polymers exhibited near-complete defluorination, whereas ultrashort side-chain fluorotelomer-based polymers were more resistant to transformation. Fluorine mass balances demonstrated that most fluorine was recovered as discovered transformation products or as unreacted fluorinated polymer under oxidizing and reducing conditions. These findings help explain the presence of PFCAs in fab wastewater and provide insights on structure-transformation relationships.