Removing PFAS from Semiconductor Manufacturing, From Resists to Rinses

By Emily Gallagher and Danilo De Simone | EE Times | April 3, 2025

Read the full article by Emily Gallagher and Danilo De Simone (EE Times)

"Per- and polyfluoroalkyl substances (PFAS) have been extensively used in various industries due to their unique properties, including resistance to heat, water, and oil. However, the persistence of these ‘forever chemicals’ in the environment and potential health risks have led to increasing regulatory scrutiny and a push toward finding alternatives. The semiconductor industry, which relies on PFAS for its unique properties in processes such as lithography and etching, is now at the forefront of this transition. Despite growing efforts to reduce PFAS use, semiconductor lithography still relies on these materials.

This article delves into the efforts and challenges faced by the semiconductor industry, particularly through the lens of imec’s initiatives, to eliminate PFAS from their materials.

Collaboration drives progress toward PFAS-free lithography materials

Imec began working with partners after a push from key industry players to find PFAS-free alternatives for lithography materials in the summer of 2023. Initially focused on chemically amplified resists (CAR) for extreme ultraviolet (EUV) lithography, the scope soon expanded to include deep UV (DUV) lithography, as well as other materials such as rinses and underlayers. To assess feasibility, imec engaged material suppliers, starting with a low-profile approach aimed at shortening PFAS chains. Encouraging early results led to a more ambitious target: achieving PFAS-zero materials, with the first phase centered on PFAS-free CAR for EUV lithography.

Sources of PFAS in CAR

In CAR, PFAS-containing compounds are primarily found in the photoacid generator (PAG), a key component that drives the resist’s chemical reaction. Fluorinated groups in PAGs help control acid diffusion, improve film uniformity, and lower surface energy, ensuring smooth coating and high-resolution patterning. Additionally, certain polymers in the resist formulation may contain PFAS in the form of fluorinated functional groups, such as trifluoromethyl (-CF₃), which contribute to solubility control and chemical stability. Beyond the polymer and PAG, other resist components may also introduce PFAS, depending on the formulation. For example, photo-decomposable quenchers (PDQs), which regulate acid diffusion and reaction kinetics, may contain varying levels of PFAS."