Document vVr4L7kO6VXdJGE5RwgZYQJdY

SEMITM Assessment of Proposed Alternatives for Fluoroelastomers in Sealings Many semiconductor manufacturing processes are very complex, with most utilizing elevated temperatures as well as aggressive and potentially hazardous chemistries that Kumagai (1990) notes require special system design considerations. Semiconductor manufacturing processes therefore require high performance seal materials that have high operating temperature range capabilities and that are also resistive to the aggressive chemistry used as process media as well as system cleaning solutions between process steps (Wang & Legare 2007). As noted by Goto et al. (2020), perfluoroelastomers (FFKM) and fluoroelastomers (FKM) have been reliable seal materials used in semiconductor manufacturing processes because of their excellent performance under these aggressive temperature and chemical conditions. Alternative materials such as EPDM and other hydrocarbon elastomers, Nitrile, as well as Silicone lack the combined acid resistivity, solvent resistivity and the high temperature performance characteristics needed in semiconductor process applications compared to perfluoroelastomers and fluoroelastomers (Foggiato, Thrash, Freerks, and Al-Saleem, 2007), a position broadly supported by material compatibility recommendations in Pruett (2005). As a result, EPDM, Silicone, and hydrocarbon elastomer materials are not technically viable substitutable sealing materials to perfluoroelastomer and fluoroelastomer in semiconductor manufacturing processes. This position is further supported by a review of non-PFAS alternatives suggested by the dossier submitters for several specific semiconductor processes shown below: Table: list of non-PFAS alternatives suggested for Fluoroelastomer's sealing applications in Appendix E2 to the Annex XV Report # Substance name Cas no EC no 1 Ethylene propylene diene monomer (EPDM) 308064-28-0 920-736-4 2 Silicone rubbers 3 Aryl Ketone polymer (PEEK) 29658-26-2 608-392-0 4 Hydrocarbon elastomers EPDM (#1) and Hydrocarbon elastomers (#4) For wet environments typically used in semiconductor manufacturing equipment for wafer surface cleaning/preparation, photolithographic material coating/developing, chemical mechanical polishing (CMP), and electrochemical deposition processes, EPDM or other hydrocarbon elastomers (such as IIR, NBR, SBR as defined in DIN/ISO 1629) cannot substitute fluoroelastomer O-rings and gaskets for the following reasons: Wafer contamination: The cleanliness level of these materials is low and the leaching out of metals and other elements from the elastomer results in metal contamination on the wafer thus making the chips unusable. Chemical incompatibility: These materials are not compatible with many of typical chemicals used in wet applications including strong acids such as, nitric, sulfuric, and hydrofluoric acids, oxidizers and solvents. This is publicly known information that is easily found in manufacturer's literature (handbooks, datasheets, etc. for example "Parker o-ring handbook") and also supported by material compatibility recommendations in Pruett (2005). Safety/environment protection: These materials lack of chemical compatibility can result in leaks, which increases the risk of human exposure and environmental release of the hazardous chemicals. Impact to production: Use of EPDM or other hydrocarbon elastomers as seals make it impossible to manufacture chips due to wafer contamination and lack of chemical compatibility. For vacuum processes' environment typically used in semiconductor manufacturing equipment for plasma etching, chemical /physical vapor deposition, and thermal processes, EPDM or other hydrocarbon elastomers cannot substitute fluoroelastomer O-rings and gaskets for the following reasons: Wafer contamination: The cleanliness level of these materials is low and some hydrocarbon's outgassing drastically increases at high temperatures, so the transfer of contaminants from the seal to the wafer will result in contamination on the wafer thus making the chips unusable. Also due to poor chemical compatibility, reaction products generated upon exposure to process gases and reactive species will result in wafer contamination, making the chips unusable.  Incompatibility with reactive gases, high temperature (for instance, max operating temperature of EPDM is up to 175C , which is more than 150C lower than FFKM's), and plasma: EPDM and other Hydrocarbon elastomers are not compatible with reactive gases and plasma, so reaction products generated upon exposure to process gases/plasma will result in wafer contamination thus making chips unusable. Safety/environment protection: These materials lack of compatibility with reactive gases and plasma can result in leaks, which increases the risk of human exposure and environmental release of the hazardous chemicals. Impact to production: Use of EPDM or other hydrocarbon elastomers as seals make it impossible to manufacture chips due to wafer contamination and lack of chemical compatibility. Breach of seal due to incompatibility can also result in breach of vacuum environment simultaneously which can, in turn, cause breakage of turbo molecular pump. It takes days to return the processing equipment to normal operation from such incident and requires many test wafers and other resources for requalification procedures. Silicone rubbers (#2) For wet environment silicone rubbers cannot substitute fluoroelastomer O-rings and gaskets because of: Wafer contamination: The cleanliness level of these materials is low and the leaching out of metals and other elements from the rubber results in contamination on the wafer thus making the chips unusable. Chemical incompatibility: These materials are not compatible with strong acids, bases, oxidizers and solvents. This is publicly known information that is easily found in manufacturer's literature and also supported by material compatibility recommendations in Pruett (2005). Safety/environment protection: These materials lack of chemical compatibility can result in leaks, which increases the risk of human exposure and environmental release of the hazardous chemicals. Impact to production: Use of silicone rubbers as seals make it impossible to manufacture chips due to wafer contamination and lack of chemical compatibility.  For vacuum processes' environment silicone rubbers cannot substitute fluoroelastomer seals because of: Wafer contamination: The cleanliness level of these materials is low, so the transfer of contaminants from the seal to the wafer will result in metal contamination on the wafer. Additionally, silicone rubbers are known to outgas volatile organic compounds (e.g., siloxanes), which results in organic contamination on the wafer. both metal contamination and organic contamination make the chips unusable. Incompatibility with reactive gases and plasma: Silicone rubbers are more resistant to reactive gases than hydrocarbons but still erode much faster than FFKM. Both characteristics result in shorter maintenance intervals and reduced productivity. Safety/environment protection: These materials lack of compatibility with reactive gases and plasma can result in leaks, which increase the risk of human exposure and environmental release of the hazardous chemicals. Silicone rubber's porous structure allows unwanted permeation of reactive gases to adjacent higher vacuum chamber, resulting in elevated safety risks as high vacuum chamber may not be designed to accept reactive gases. Environmental concerns of the substitute itself or potential "regrettable substitution": Low MW siloxanes especially D4, D5, D6 are considered to have some POPs properties. Si rubbers are known to contain siloxanes that are residual originated from its unreacted source materials. Information regarding typical concentration level of siloxanes (sum of D4-D10) in final silicone rubber product (e.g., silicone rubber sheet) can be found in manufacturer's literature (handbooks, datasheets, etc. for example "Silicone rubber quality" by Kyowa-kogyo corporation). Reported level is in the order of several tens to hundred ppm after an additional high temperature curing process (e.g., 250C, 4hours). Impact to production: Use of silicone rubber as seals make it impossible to manufacture chips due to wafer contamination, lack of chemical compatibility, and operability issues such as gas permeation. PEEK (#3) While PEEK is known to be used for sealing viscous and abrasive materials in some industries, its very low elasticity and flexibility is not suitable for sealing off less viscous fluids or sealing between differential pressure (e.g., sealing between vacuum and atmosphere, pressurized fluid at mechanical joints of piping), which are the case for most of sealing applications in semiconductor manufacturing uses. In addition, Peek being a rigid material, it is not always possible to retrofit into the hardware designed for elastomers. For wet environments typically used in semiconductor manufacturing equipment for wafer surface cleaning/preparation, PEEK cannot substitute fluoroelastomer O-rings and gaskets because of: Chemical incompatibility: These materials are not compatible with certain chemicals used in wet applications including strong acids such as, nitric, sulfuric, and hydrofluoric acids. This is publicly known information that is easily found in manufacturer's literature (handbooks, datasheets, etc. for example "Curbell Chemical Resistance") and also supported by material compatibility recommendations in Pruett (2005). Additional discussion on fluoroelastomer performance requirements can be found throughout SIA PFAS Consortium White Paper: PFAS-Containing Articles used in Semiconductor Manufacturing and Table 3 in Appendix III of the White Paper attached to this submittal or can be obtained online at: https://www.semiconductors.org/pfas/ References Foggiato, J., Thrash, A., Freerks, F., & Al-Saleem, F. (2007) "Optimization of semiconductor manufacturing equipment seals for enhanced performance," 2007 International Symposium on Semiconductor Manufacturing, Santa Clara, CA, USA, 2007, pp. 1-4, doi: 10.1109/ISSM.2007.4446847. Goto, T., Obara, S., Shimizu, T., Inagaki, T., Shirai, Y., & Sugawa, S. (2020). Study of CF4/O2 Plasma resistance of o-ring elastomer materials. Journal of Vacuum Science and Technology, (38)1. https://doi.org/10.1116/1.5124533 Kumagai, H.Y. (1990). Hazardous gas handling in semiconductor processing. Journal of Vacuum Science & Technology, (8),3, 2865-2873. Pruett, K. (2005). Chemical Resistance Guide for Elastomers III: A Guide to Chemical Resistance of Rubber and Elastomeric Compounds (III). Compass Publications. Wang, S., & Legare, J. M. (2003). Perfluoroelastomer and fluoroelastomer seals for semiconductor wafer processing equipment. Journal of Fluorine Chemistry, 122(1), 113-119. https://doi.org/10.1016/S0022-1139(03)00102-7 "Curbell Chemical Resistance" available at https://www.curbellplastics.com/wpcontent/uploads/2022/11/Chemical-Resistance-Chart.pdf "Silicone rubber quality" by Kyowa-kogyo corporation, available at https://www.kyowakg.com/quality/2ndkaryu/