Challenges and progress of PFAS alternatives for ArF resist

Perfluoroalkyl substances (PFAS) are highly persistent in the environment and significantly contribute to the ecotoxicity of soils and organisms. Due to their severe environmental impacts, they have drawn significant attention from regulatory authorities over the past several decades. In semiconductor manufacturing, PFAS additives are commonly used in photoresists to secure the lithography performance for achieving decent yield. However, for the contribution to more sustainable semiconductor technologies, Fujifilm aims to eliminate PFAS from advanced resists. As Negative-tone development (NTD) system with using organic solvent, which was devised by Fujifilm, has been long and largely contributed to semiconductor technology in immersion ArF(ArFi), our first target of PFAS elimination would be ArFi NTD resists. To achieve critical lithography performance and defect performance in ArFi resists, PAGs and immersion additives are the keys. These compounds are typically PFAS, thus replacement with PFAS alternatives is essential and challenge. In this paper, how to achieve the decent acidity in PFAS-free PAGs and how to control the hydrophobicity of resist surface in PFAS-free immersion additives are described. The achievement of our PFAS-free resist was equivalent patterning performance on 90nm pitch Line and Space pattern with similar contact angle compared to the conventional one, suggesting that advanced PFAS-free resist for ArFi NTD is realized with promising manner. On the other hand, to realize PFAS-free in ArFi positive-tone development (PTD) with alkaline based developer, achieving both immersion compatibility and alkali developability is required and considered to be the most challenging aspect. The latest approach for ArFi PTD will be reported as well.