Onium salts, widely used as photoacid generators (PAGs) in the semiconductor industry, are receiving increased regulatory scrutiny due to their potential hazardous properties. Evaluating the environmental impacts of these chemicals requires knowledge of the fate of the onium species during photolithography steps, which remains unclear for many PAGs. The current study investigated the fate of five representative onium PAGs using an irradiation setup simulating industrial photolithography. All onium compounds reacted rapidly under 254 nm irradiation with high quantum yields (0.23−0.85). Multiple highly aromatic and hydrophobic photoproducts were characterized using HPLC-DAD and GC-MS; eight PAG photoproducts were identified for the first time. A homolytic reaction mechanisms is proposed and discussed. Additionally, we found that selected photoproducts had remarkably higher acute microbial toxicity toward bacterium <i>Allivibrio fischeri</i> compared to the onium cations. Also, based on octanol-water partition coefficients, the photoproducts were substantially more hydrophobic than the parent compounds. The results fill a critical data gap hindering the environmental impact assessment of onium PAGs, and provide clues on potential management strategies for both onium compounds and their photoproducts.

Photochemical fate of onium photoacid generator cations under photolithography relevant UV irradiation and environmental risk properties of photoproducts

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