Treatment of PFAS substances in lithography

PFAS substances are widely used in lithography processes. PFAS substances are expected to be replaced with alternative substances due to concerns of environmental pollution, but it is anticipated that long-term research and development will be necessary in semiconductor use. In this paper, we focused on triphenylsulfonium perfluoro-1-butanesufonate (TPS-PFBS), which is a type of PFAS that is widely used as a photoacid generator (PAG), and we attempted to concentrate this chemical from model waste liquids. Small-scale experiments for a concentration system were performed with a special hollow fiber membrane and a special ion exchange resin. The hollow fiber membrane could partially filter the PFBS, and the hollow fiber membrane can be expected to require low maintenance. The ion exchange resin could remove PFBS with high collection rate but requires high maintenance. As a result, it is expected that waste liquid can be separated into PFAS free solvent and concentrated waste when this system using both hollow fiber and ion exchange resins is realized in large scale application. We believe that when this system is used for recycling solvents, it will not only concentrate PFAS but also contribute to CO₂ reduction towards a net-zero society.