Review of essential use of fluorochemicals in lithographic patterning and semiconductor processing

Ober, Christopher K.; Käfer, Florian; Deng, Jingyuan

doi:10.1117/1.jmm.21.1.010901

Cited by 18 publications

(49 citation statements)

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“…Short-and ultrashort-chain PFSAs are major constituents of photoresists and are used as the counter anion in many types of photoacid generators. 9 Here, we measured PFBS and TFMS at relatively high concentrations (70−175 ng L −1 ) across all three fabs, suggesting these are counter anions in the photoacid generators used in these fabs. Despite this known source of PFSAs, the PFCAs make up over 90% of the total PFAS concentration measured in all three fabs.…”

Section: ■ Results and Discussionmentioning

confidence: 67%

“…PFCAs are not known to be common anions in photoacid generators, nor are they key constituents used in other photolithography materials. 9 Therefore, it is likely that PFCAs are transformation products of other constituents that were generated during photolithography or other fab processes. Lastly, the fab3 samples are from the effluent of an onsite reverse osmosis system used to treat fab wastewater.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…23−28 Trifluoromethanesulfonate (TFMS), the PFSA with one fluorinated carbon, is a known constituent of photoresists used in semiconductor manufacturing. 9,29 In addition to the industrial shift to short-and ultrashort-chain PFASs, ultrashort-chain PFASs are terminal end products from transformations of fluorinated materials in the environment and in the total oxidizable precursor assay. 30−32 Furthermore, larger quantities of short-and ultrashort-chain PFASs must be used to match the technical performance of long-chain PFASs, ultrashortchain PFASs are highly soluble and mobile in the environment, and traditional water treatment technologies are ineffective for these small compounds.…”

Section: ■ Introductionmentioning

confidence: 99%

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Rapid and Simultaneous Quantification of Short- and Ultrashort-Chain Perfluoroalkyl Substances in Water and Wastewater

Jacob

Helbling

2022

ACS EST Water

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Per-and polyfluoroalkyl substances (PFASs) are a class of chemicals of growing concern. Recently, there has been a shift toward the use of short-and ultrashort-chain PFASs, which are difficult to measure with current analytical methods and rarely included in environment monitoring studies. In this research, we developed and optimized online solid-phase extraction, highperformance liquid chromatography, and electrospray ionization high-resolution mass spectrometry methods for the rapid and simultaneous quantification of 10 short-and ultrashort-chain PFASs. We applied our method to water samples collected from a variety of natural, engineered, industrial, and commercial water systems. We detected ultrashort-chain PFASs in every sample, including hydraulic fracturing water and wastewater samples and wastewater from electronic fabrication facilities for the first time, identifying previously unknown sources of ultrashort-chain PFASs. We also measured ultrashort-chain PFASs in a variety of drinking water sources, including what was thought to be pristine groundwater and surface water sources. The measurement of ultrashortchain PFASs in every sample type studied here raises concern over the potential ubiquity of these compounds in the environment and highlights the need for further monitoring studies, especially as longer-chain PFASs become regulated, and the industrial shift to short-and ultrashort-chain PFASs increases.

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Section: ■ Results and Discussionmentioning

confidence: 67%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Rapid and Simultaneous Quantification of Short- and Ultrashort-Chain Perfluoroalkyl Substances in Water and Wastewater

Jacob

Helbling

2022

ACS EST Water

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“…The acid generated by PAGs 3–8 was retained as 4-bromobenzenesulfonic acid (p K a −3.1) because it had been sufficient to depolymerize Br- l PPA under DUV exposure based on the results of PAG 4 . It was also appealing as very few EUV resists have been able to avoid using fluorinated acids, which are of significant environmental concern. − We systematically designed PAGs 3 – 8 to possess a wide range of electron affinities and bond strengths to evaluate the relationship between chemical structure and EUV sensitivity. As we sought to elucidate the sensitivity trend of PAGs 3–8 , the dependence of Br- l PPA’s dose-to-clear on the concentration of PAGs generating 4-bromobenzenesulfonic acid was evaluated.…”

Section: Results and Discussionmentioning

confidence: 99%

High-Performance Chain Scissionable Resists for Extreme Ultraviolet Lithography: Discovery of the Photoacid Generator Structure and Mechanism

et al. 2022

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Extreme ultraviolet (EUV) lithography currently dominates the frontier of semiconductor fabrication. Photoresists must satisfy increasingly strict pattern fidelity requirements to realize the significant enhancements in resolution offered by EUV technology. Traditional chemically amplified resists (CARs) have hit a barrier in the form of the resolution, line edge roughness, and sensitivity trade-off. This has been compounded by a lack of understanding of the chemical mechanism associated with the EUV process. Here, we synthesize a series of novel EUV photoresists based on a self-immolative, acid-labile poly(acetal) system. These systems are shown to be commercially viable under current EUV requirements. Careful study of the resists’ degradation pathways has enabled the identification of a remarkable photoacid generator (PAG) that functions as both an acid generator and base quencher, enabling further improvements over previous resists. density functional theory calculations reveal, for the first time, the connection between the PAG activation barrier and resist sensitivity and suggests why attempts to use electron-beam lithography to predict EUV performance have failed.

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“…We anticipated that a sufficiently electron-withdrawing substituent could destabilize the nitrilium intermediate. A trifluoromethyl group was selected for this purpose with the added benefit of increasing the EUV absorption cross section , of the PAG. Fortuitously, we found PAG 2 to be completely bench-stable for more than 2 years.…”

Section: Resultsmentioning

confidence: 99%

Modular Synthesis of Phthalaldehyde Derivatives Enabling Access to Photoacid Generator-Bound Self-Immolative Polymer Resists with Next-Generation Photolithographic Properties

et al. 2022

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The resolution, line edge roughness, and sensitivity (RLS) trade-off has fundamentally limited the lithographic performance of chemically amplified resists. Production of next-generation transistors using extreme ultraviolet (EUV) lithography depends on a solution to this problem. A resist that simultaneously increases the effective reaction radius of its photogenerated acids while limiting their diffusion radius should provide an elegant solution to the RLS barrier. Here, we describe a generalized synthetic approach to phthalaldehyde derivatives using sulfur(VI) fluoride exchange click chemistry that dramatically expands usable chemical space by enabling virtually any non-ionic photoacid generator (PAG) to be tethered to phthalaldehyde. The resulting polymers represent the first ever PAG-tethered self-immolative resists in an architecture that simultaneously displays high contrast, extraordinary sensitivity, and low roughness under EUV exposure. We believe this class of resists will ultimately enable researchers to overcome the RLS trade-off.

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Review of essential use of fluorochemicals in lithographic patterning and semiconductor processing

Cited by 18 publications

References 0 publications

Rapid and Simultaneous Quantification of Short- and Ultrashort-Chain Perfluoroalkyl Substances in Water and Wastewater

Rapid and Simultaneous Quantification of Short- and Ultrashort-Chain Perfluoroalkyl Substances in Water and Wastewater

High-Performance Chain Scissionable Resists for Extreme Ultraviolet Lithography: Discovery of the Photoacid Generator Structure and Mechanism

Modular Synthesis of Phthalaldehyde Derivatives Enabling Access to Photoacid Generator-Bound Self-Immolative Polymer Resists with Next-Generation Photolithographic Properties

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