Impact of Supply Chain Conditions on IPA Product Quality
The IRDS roadmap outlines technology requirements for surface contamination control, specifying that isopropyl alcohol (IPA) used in semiconductor manufacturing must meet purity levels of <0.008 ppb for trace metals and <20 ppb for trace organics by 2026 [1]. As device nodes continue to shrink, the level of allowable impurities is expected to decrease. This paper reports on the impact of materials used throughout the IPA supply chain on the purity of IPA delivered to semiconductor fabs. Specifically, we present data on contaminants introduced through interactions between IPA and materials used in its storage and transportation from the producer to the fab. Traditionally, IPA has been stored in HDPE-lined tanks at the production plant, then transported in HDPE-lined ISO’s or drums from the producer to the fabs. Previous studies have shown that IPA can leach trace organics—including high–molecular weight phthalates and phosphates—from HDPE containers [2]. These contaminants, due to their high boiling points, can remain on wafer surfaces after cleaning and drying, potentially leading to surface defects [3,4]
To minimize organic contamination from HDPE, stainless steel (SS) ISO containers may be used for IPA transport. While stainless steel may potentially prevent organic leaching, it may introduce trace metal contamination. To evaluate this risk, we conducted experiments investigating both trace metal and trace organic leaching from electropolished 316L stainless steel (EP 316L SS) containers. Experiments were conducted using 110 mL 316L SS containers which were electropolished to 10RA finish. Containers were kept at different temperatures, 0°C, 24°C and 50°C. Samples were analyzed every 2 weeks for trace metals and organics. Trace metals & elemental speciation experiments were performed using Elemental Scientific’s (ESI) prepFAST IC which uses an ICPMS detector. Traditional ion chromatogram was performed utilizing ESI’s SGTX IC. Trace organic analysis was performed using ESI’s prepFAST CARBON, which uses an electrospray QTOF-MS as a detector. Nanoparticle analysis was performed using ESI’s microFAST SingleCell which also uses an ICPMS as a detector. IC separation allows the determination of different forms of Cr in the leachate. IC can separate Cr(III), Cr(VI) and organic bound chromium.
The results indicate that organic bound Cr is generated, presumably from the reaction of IPA and the Cr rich surface of the EP SS container. Organic Cr is observed in the leachates at 25°C and 50°C, whereas the leachate from the containers stored at 0°C do not indicate the presence of organic bound Cr after 8 weeks. Our results also indicate that some organic contaminants can also be formed during the interaction of the IPA with the EP 316L SS surface. Isopropyl Hydrogen Sulfate (C3H8O4S) is present at trace levels in the IPA stored in the SS container at 50°C. Our results will shed light on the impact of using SS ISO’s in the supply chain. The results will also provide insight into the possibility of preparing the SS ISO’s so that the impact of leaching from the SS surface.
REFERENCES:
[1] International Roadmap for Devices and Systems, 2022 Update, Yield Enhancement, pp 21.
[2] Brianna Dufek, Suhas Ketkar, Austin Schultz, Kyle Uhlmeyer, Jake Unnerstall, “Determination of trace level organic contamination leached from HDPE containers used for semiconductor solvents and recovery and identification of organic residues on wafer surfaces using these contaminated solvents”, 2023 UltraPure Micro, Austin, TX
[3] B. Dufek et al., ""Rapid Analysis of Organic Contaminants in Semiconductor Process Chemicals and on Wafer Surfaces,"" 2024 35th Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC), Albany, NY, USA, 2024, pp. 1-6, doi: 10.1109/ASMC61125.2024.10545524.
[4] Andres Villalpando, Brianna Dufek, ”Criticality of Modern Analytical in Semiconductor Grade IPA Analysis: Impacts of Construction Compatibility and Supply Chain Conditions on Product Integrity”, 2025 UltraFacility , Austin, Tx.
BIOGRAPHY
Suhas is a veteran analytical expert in the semiconductor industry who has over 40 years’ experience in the analysis of trace contaminants. He began his career at Extrel Corporation in 1985 as a Staff Physicist developing mass spectrometer based instrumentation for trace analysis of environmental contaminants. During his time at Extrel he also developed instrumentation to measure sub ppt contaminants in semiconductor grade bulk inert gases. He joined Air Products and Chemicals in 1991 and developed novel approaches to utilize Ion Mobility Spectrometers for the analysis of semiconductor grade gases.
Over the next decade he developed a methodology to analyze trace contaminants in specialty gases and semiconductor liquid chemicals. He was the Director of Global Analytical Technology at Versum Materials after the company was spun off from Air Products and Chemicals. He retained this position when Versum Materials was later acquired by Merck KGaA, Darmstadt, Germany and retired from there at the end of 2023. He currently works at Elemental Scientific, a company providing automation tools for online analysis of semiconductor chemicals.
Suhas is active on the SEMI Liquid Chemicals Committee and the Analytical Task Force. Suhas has a PhD in Physics from the University of Texas at Austin and an Executive Master’s in Technology Management from Wharton/UPenn.