Patterning performance of perfluoroalkyl substances (PFAS) free EUV chemically amplified resists: a step towards environmentally friendly lithographic chemicals

Per- and Polyfluoroalkyl Substances (PFAS) are notorious for their persistence in the environment, earning the label forever chemicals. They contribute significantly to the eco-toxicity of soils and living organisms and, because of such severe environmental impact in the last decades, they have garnered significant attention from regulatory authorities. PFAS are prevalent across various industries, including semiconductor manufacturing, and necessitates exploration of PFAS-free alternatives. In semiconductor production, PFAS additives are commonly used in photoresists, thus PFAS-free solutions in lithography can represent a significant advancement for more sustainable device technology. At imec we prioritize process development by quantifying the environmental impacts of IC chip manufacturing using impact factors like carbon emissions, energy use, material scarcity and toxicity. Photoresist use in manufacturing flows is a significant contributor to environmental toxicity. Any new technology requires a long development cycle before adoption is possible in the fab. Responsible development demands that we prioritize the most challenging and most impactful applications for PFAS-free material development and lithography qualifies in both cases. It is in such a context that imec started in 2023 a project focused on PFAS-free Chemically Amplified Resists (CAR) with core focus on materials for Extreme Ultraviolet Lithography (EUVL). In this work, the imec project framework is deployed with end targets of removing the environmental impact from PFAS chemicals while maintaining equivalent patterning performance achieved using current EUV CAR state-of-the-art photo chemicals. The best patterning performance of PFAS-free EUV CAR are discussed for pitch 32nm dense line-space patterns and pitch 36nm dense hexagonal contact hole applications.