Chips Built with Forever Chemicals

Semiconductor fabrication relies on per- and polyfluoroalkyl substances (PFAS) — persistent "forever chemicals" — in critical process steps: photolithography (photoacid generators), plasma etching (fluorinated gases), chemical-mechanical polishing (surfactants), and cleanroom equipment (fluoropolymer seals and tubing). SEMI estimates PFAS are used in >50% of critical chip fabrication steps. No viable PFAS-free alternatives match the performance of current PFAS-based materials for these applications. With incoming EPA and EU REACH regulations threatening to restrict chemicals essential to chip production, the industry faces a potential manufacturing crisis.

The global semiconductor industry generates >$600 billion in annual revenue and underpins the entire digital economy. PFAS contamination near semiconductor fabs has triggered >$50 billion in environmental litigation and cleanup costs across industries. The proposed EU universal PFAS restriction could directly affect chip production in European fabs. TSMC alone uses ~10 million liters of PFAS-containing chemicals annually. NSF DCL 24-043 explicitly calls out "eliminating harmful chemicals like PFAS in semiconductor manufacturing" as an engineering frontier. A manufacturing disruption from PFAS regulation without alternatives could cascade through the entire electronics supply chain.

Some fluorinated etching gases (SF6, NF3, C4F8) have alternatives under development, but none match the etch selectivity and profile control of current processes. EUV photolithography resists contain fluorinated polymers essential for the chemically amplified resist mechanism — alternative resist chemistries (metal-oxide, molecular resists) are 5–10 years from production readiness. Fluoropolymer seals and tubing have no replacements that resist the chemical environments in wet processing tools. Some PFAS-containing surfactants in CMP slurries have been replaced with shorter-chain alternatives, but these still contain fluorine and may fall under future regulation. The fundamental problem is that PFAS are used precisely because of the properties that make them persistent — extreme chemical stability, low surface energy, and thermal resistance.

Discovering new chemical functionalities that match C–F bond properties (stability, hydrophobicity, low surface energy) in process conditions (high temperature, plasma, aggressive solvents) without environmental persistence. This likely requires entirely new classes of materials rather than incremental modifications of existing fluorinated compounds. Alternative approaches include redesigning fabrication process steps to eliminate the need for PFAS-dependent functions entirely — for example, dry processes replacing wet chemical steps that require fluorinated surfactants.

A student team could map the PFAS dependency tree for a specific semiconductor process step (e.g., CMP slurry formulation), identifying which PFAS properties are strictly necessary and which could be achieved through alternative chemistry. Alternatively, a team could evaluate non-fluorinated polymer seals for resistance to specific semiconductor wet-bench chemicals, generating compatibility data that the industry needs. Relevant skills: polymer chemistry, surface science, materials engineering, semiconductor process engineering.