PFAS-Free EUV Photoresist Explained — PatSnap Eureka
PFAS-Free EUV Photoresist: What It Is and Why It Matters
Regulatory pressure from the U.S. EPA, EU REACH, and South Korea's KSCA is forcing the semiconductor industry to eliminate fluorinated chemistries from EUV lithography. Metal-containing photoresists and carbon-based pellicle materials are the emerging alternatives — here's what the patent data reveals.
PFAS in EUV Photoresist: A Regulatory and Physics Collision
Traditional deep-ultraviolet (DUV) chemically amplified resists (CARs) have long relied on fluorinated polymer backbones and fluorinated photoacid generators (PAGs) to achieve the etch resistance, hydrophobicity, and line-edge roughness (LER) performance required for sub-100 nm patterning. Fluorinated top-coat layers — closely related to the same PFAS chemical families — have also been applied to protect photoresist layers from environmental contamination during lithographic processing.
PFAS compounds — defined by the presence of at least one fully fluorinated carbon atom — are now subject to sweeping regulatory restrictions globally. The U.S. EPA's 2024 PFAS drinking water rules, the EU REACH consortium restriction proposal covering thousands of PFAS substances, and South Korea's Chemical Substances Control Act (KSCA) amendments collectively threaten the supply chain viability of fluorinated PAGs, fluorinated surfactants used in resist formulation, and fluorinated top-coat polymers.
For semiconductor fabs operating in all three jurisdictions, this creates an urgent materials substitution imperative affecting EUV photoresist supply chains specifically, because EUV nodes (5 nm, 3 nm, 2 nm) represent the highest-volume consumption points for these specialty fluorochemicals. The advanced materials intelligence required to navigate this transition is substantial — spanning chemistry, process engineering, and IP strategy simultaneously.
Critically, fluorine-containing polymers can outgas fluorine radicals under EUV irradiation, contaminating optics and degrading mirror reflectivity — a process-level problem that compounds the regulatory toxicity concern. This means EUV physics itself mandates fluorine-free materials, independent of any regulatory driver.
Metal-Containing Photoresists: The Primary EUV Alternative
The most technically mature PFAS-free pathway for EUV lithography is the metal-containing photoresist (MCR), also called organometallic oxide resist. Hafnium- and tin-oxo cluster chemistries absorb EUV photons efficiently through metal centers — no fluorinated PAGs required.
UV Pre-Cure for Lower EUV Dose
Lam Research's 2022 patent discloses exposing an organometallic oxide film to blanket UV treatment prior to lithographic patterning. The UV pre-cure shifts the solubility curve of the film, allowing a lower EUV dose to be used for patterning, and additionally hardens the film post-development — addressing dose sensitivity and pattern collapse without any fluorinated chemistry. This is a direct functional equivalent to the role traditionally played by fluorinated hardening agents in CAR formulations.
Eliminates fluorinated hardening agentsMulti-Stage Dry Post-Exposure Bake
A 2024 Lam Research patent details a multi-step post-exposure bake (PEB) protocol for metal-containing photoresists. The process involves a first bake in an oxygen-rich atmosphere at moderate temperature, followed by a second bake in inert gas at significantly elevated temperature. This dual-atmosphere PEB improves etch selectivity in dry development — entirely avoiding aqueous solvent steps where fluorinated surfactants are conventionally consumed.
Dry development — zero fluorinated developerDry Development as Systemic PFAS Exit
The shift to dry development is itself a PFAS elimination strategy, since fluorinated surfactants in aqueous developer are a major PFAS discharge point in conventional semiconductor fabs. The dry development compatibility of metal-containing resists eliminates not only the fluorinated PAG but also the fluorinated surfactant, the fluorinated top-coat, and the fluorinated rinse agents in a single materials platform transition.
Single transition eliminates 6 PFAS touchpointsEUV Physics Mandated Fluorine-Free Design Early
ASML's 2008 EUV substrate coating patent explicitly acknowledged that fluorine-containing polymers can outgas fluorine radicals under EUV irradiation, contaminating optics and degrading mirror reflectivity. The design space described deliberately moves away from fluorinated protection layers — a physics constraint that preceded but now reinforces regulatory PFAS restrictions. This patent established early design principles for non-fluorinated EUV top coats using atoms of beryllium, boron, carbon, silicon, zirconium, niobium, and molybdenum.
Physics constraint predates regulationEUV PFAS-Free Innovation: What the Patent Data Shows
Two key dimensions from the 24-record patent dataset: pellicle material transmittance performance and the distribution of innovation activity across technology categories.
PFAS-Free EUV Pellicle Materials — Minimum Transmittance
All four dominant PFAS-free pellicle material families achieve a minimum EUV transmittance of at least 92%, demonstrating that fluorine elimination does not compromise optical performance.
EUV PFAS-Free Patent Activity by Technology Category
The 24-record dataset splits across pellicle membrane materials, photoresist processing, EUV apparatus/optics, and process inspection — all converging on PFAS-free approaches.
PFAS-Free EUV Pellicle Materials: A Completed Transition
The EUV pellicle patent portfolio has already converged on PFAS-free materials — fluorinated polymer membranes are incompatible with EUV due to outgassing. This provides a proven model for how the photoresist ecosystem is evolving.
Carbon Nanofiber Films — Lintec of America
Lintec of America describes filtration-formed nanostructured films comprising randomly intersected carbon nanofibers with thickness from 3 nm to 100 nm and minimum EUV transmittance of at least 92% — performance parameters achieved with pure carbon chemistry and no fluorine. Annealing protocols in inert gas or vacuum further enhance EUV transmission and reduce scattering.
Boron Nitride Nanotube Membranes — FST Co., Ltd.
FST Co., Ltd. pursues boron nitride nanotube (BNNT) membranes via plasma-assisted CVD synthesis using only boron and nitrogen precursors. Three related patents (2024, 2025, 2026) describe the manufacturing apparatus and include a charge-forming layer on the membrane base layer — all achieved without fluorinated surface treatments.
Fluorinated CAR vs. Metal-Containing PFAS-Free Resist: Head-to-Head
A direct comparison across eight dimensions, derived from patent analysis of Lam Research, ASML, and industry literature on EUV photoresist chemistry.
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Key Players Shaping PFAS-Free EUV Innovation
The patent data reveals a well-defined competitive landscape structured around photoresist processing and pellicle membrane materials — both axes converging on PFAS-free approaches driven by EUV physics constraints and regulatory pressure.
Lam Research Corporation
The most active filer on PFAS-free resist processing in the dataset, with two patents (2022, 2024) establishing a process architecture around organometallic oxide films with UV pre-cure and multi-stage dry PEB. Their approach bypasses fluorinated chemistry at every process step — formulation, exposure, development, and bake — making it the most comprehensive PFAS elimination strategy in the dataset. The IP analytics around their filing strategy reveals a systematic process-by-process elimination approach.
2 patents · UV pre-cure + multi-stage dry PEBASML Netherlands B.V.
ASML contributes foundational process infrastructure, including a 2008 substrate coating patent establishing early design principles for non-fluorinated EUV top coats, and a 2025 patent on EUV light source debris management using hydrogen radical generation to clean tin debris without oxygen-containing species — a fluorine-free cleaning chemistry that complements resist and pellicle PFAS-free design. ASML's work is monitored by IP teams at major fabs via platforms like PatSnap.
Foundational non-fluorinated EUV top coat principlesLintec of America · FST Co., Ltd. · TSMC
Three companies contest the pellicle membrane space with distinct material platforms: Lintec of America (carbon nanofiber, 3–100 nm thickness, ≥92% EUV transmittance), FST Co., Ltd. (boron nitride nanotube via plasma-assisted CVD), and TSMC (CNT with Joule heat treatment and sp² carbon surface modification). All have filed multiple patents from 2023 to 2026, indicating active ongoing development. This landscape is well-suited to competitive intelligence monitoring.
All achieve ≥92% EUV transmittance, zero fluorineHanyang University · IMEC
Hanyang University has filed on EUV process inspection methodologies, including a 2025 patent on comprehensive inspection equipment that measures pellicle reflectivity, transmittance, and mask imaging quality together — providing the metrology infrastructure needed to validate PFAS-free material performance in production environments. IMEC contributes EUV apparatus design focused on pellicle scattering management in EUV illumination systems. Both institutions provide the qualification infrastructure that new PFAS-free materials must pass. Developers working with PatSnap's API can integrate this patent data directly into R&D workflows.
Simultaneous reflectivity, transmittance, imaging inspectionPFAS-Free EUV Photoresist — Key Questions Answered
PFAS-free EUV photoresist refers to photoresist materials used in extreme ultraviolet lithography that contain no per- or polyfluoroalkyl substances. The leading platform is the metal-containing photoresist (MCR), also called organometallic oxide resist, which uses hafnium- and tin-oxo cluster chemistries that absorb EUV photons efficiently through metal centers without requiring fluorinated photoacid generators.
Traditional deep-ultraviolet (DUV) chemically amplified resists (CARs) have long relied on fluorinated polymer backbones and fluorinated photoacid generators (PAGs) to achieve the etch resistance, hydrophobicity, and line-edge roughness (LER) performance required for sub-100 nm patterning. Fluorinated top-coat layers have also been applied to protect photoresist layers from environmental contamination during lithographic processing.
The U.S. EPA's 2024 PFAS drinking water rules, the EU REACH consortium restriction proposal covering thousands of PFAS substances, and South Korea's Chemical Substances Control Act (KSCA) amendments collectively threaten the supply chain viability of fluorinated PAGs, fluorinated surfactants used in resist formulation, and fluorinated top-coat polymers. For semiconductor fabs operating in all three jurisdictions, this creates an urgent materials substitution imperative.
Metal-containing photoresists (MCRs), also called organometallic oxide resists, use hafnium- and tin-oxo cluster chemistries that absorb EUV photons efficiently through their metal centers without requiring fluorinated PAGs. Their inorganic character delivers high etch selectivity intrinsically. Combined with dry plasma development — which removes the aqueous developer step — MCRs eliminate fluorinated surfactants, rinse agents, and developer discharge, transforming PFAS-free resist from a materials question into a process architecture question.
Carbon nanofiber, carbon nanotube (CNT), boron nitride nanotube (BNNT), and graphene are the dominant PFAS-free pellicle material families. Lintec of America describes ultra-thin carbon nanofiber films with minimum EUV transmittance of at least 92%. FST Co., Ltd. pursues BNNT membranes via plasma-assisted CVD. TSMC has explored CNT pellicle manufacturing using Joule heat treatment. All achieve high EUV transmittance with no fluorine.
Lam Research has filed two key patents on PFAS-free resist processing. A 2022 patent discloses UV pre-cure of organometallic oxide films prior to lithographic patterning, which shifts the solubility curve and allows a lower EUV dose — addressing dose sensitivity without any fluorinated chemistry. A 2024 patent details a multi-stage post-exposure bake (PEB) with a first bake in an oxygen-rich atmosphere followed by a second bake in inert gas, improving etch selectivity in dry development and entirely avoiding aqueous solvent steps where fluorinated surfactants are conventionally consumed.
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References
- Substrate coating method for EUV lithography and substrate with photoresist layer — ASML Netherlands B.V., 2008
- Pre-exposure photoresist curing to improve EUV lithography performance — Lam Research Corporation, 2022
- Multi-stage post-exposure processing to improve dry development performance of metal-containing resists — Lam Research Corporation, 2024
- Ultra-thin, ultra-low density films for EUV lithography — Lintec of America, Inc., 2024
- Ultra-thin, ultra-low density films for EUV lithography — Lintec of America, Inc., 2023
- Extreme ultraviolet pellicle having improved extreme ultraviolet transmittance — Lintec of America, Inc., 2025
- EUV pellicle including boron nitride nanotube — FST Co., Ltd., 2025
- Apparatus for manufacturing a boron nitride nanotube membrane for EUV pellicle — FST Co., Ltd., 2024
- Pellicle for EUV lithography masks and methods of manufacturing thereof — Taiwan Semiconductor Manufacturing Company, 2024
- Pellicle for EUV lithography masks and methods of manufacturing thereof (sp² carbon) — Taiwan Semiconductor Manufacturing Company, 2024
- The manufacturing method of pellicle for protecting EUV photomask using reinforced pad — Cham Graphene Co., Ltd., 2026
- Systems, methods, and devices for cleaning target material debris from EUV containers and EUV collectors — ASML Netherlands B.V., 2025
- An extreme ultraviolet lithography device — IMEC VZW, 2022
- Comprehensive inspection equipment for EUV exposure process — Hanyang University Industry-Academic Cooperation Foundation, 2025
- Construction method of database for pellicle membrane inspection — Hanyang University Industry-Academic Cooperation Foundation, 2021
- U.S. Environmental Protection Agency — PFAS Regulations and Drinking Water Rules, 2024
- European Chemicals Agency (ECHA) — EU REACH PFAS Restriction Proposal
- World Intellectual Property Organization (WIPO) — Global Patent Filing Trends in Semiconductor Materials
All data and statistics on this page are sourced from the references above and from PatSnap's proprietary innovation intelligence platform. Patent analysis conducted via PatSnap Eureka.
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