Particle Precursors and On-Wafer Defectivity: IRDS Collaborative Research Progress and Future Directions
ABSTRACT
The concept of particle precursors—dissolved molecular compounds that can form particles when dried on wafer surfaces—as an emerging contamination risk for advanced semiconductor manufacturing, was first presented at the Surface Preparation and Cleaning Conference in 2022. A key research milestone presented was the 2021 IRDS UPW study demonstrating correlation between liquid nanoparticle sizing (LNS) measurements and on-wafer particle formation using ion exchange resin extracts on 300mm wafers, with defect verification by KLA SP7 and UNISERS inspection systems. As critical particle sizes continue to trend toward 1 nm per IRDS roadmap projections, traditional light-scattering optical particle counters cannot detect these contaminants, creating an urgent need for alternative metrology and proactive contamination control strategies.
This paper presents a three-year update on particle precursor research conducted through collaborative IRDS UPW and Critical Polymer Components Task Force initiatives and the testing performed by the SEMI UPW Task Force. Since 2022, significant progress has been achieved in understanding particle precursor sources, measurement techniques, and their impact on wafer defectivity.
In 2023, IRDS Critical Components experiments examined particle precursor generation from polymer piping materials at elevated temperatures (85°C), revealing composition-dependent risks between PFA and PVDF materials in hot UPW service. These studies have informed development of SEMI F121, the Guide for Evaluating Metrology for Particle Precursors in Ultrapure Water, published in September 2023, which provides standardized performance criteria for qualifying particle precursor measurement techniques.
Research has identified primary particle precursor sources including ion exchange resins (the predominant contributor), membrane filters, membrane contactors, and polymer piping—particularly in elevated temperature UPW applications. Liquid chromatography-organic carbon detection (LC-OCD) has proven valuable for molecular weight characterization of these dissolved species, enabling better understanding of which organic fractions pose the greatest particle formation risk. Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) and other vibrational spectroscopy have demonstrated the ability for identifying the chemical composition of the particle precursors found in semiconductor grade UPW.
The presentation will also review data generated from ongoing testing and planned experiments designed to further characterize particle formation pathways and quantify defectivity risks. Future testing will examine the relationship between particle precursor concentration, molecular composition, contaminant adhesion and resulting on-wafer defects across different process conditions, with the goal of establishing predictive models for yield impact assessment and methods for industry development. This work supports the semiconductor industry's transition from reactive particle monitoring to proactive contamination prevention, aligning with IRDS roadmap recommendations for advanced node manufacturing where killer particle sizes have exceeded the detection capabilities of conventional metrology.
BIOGRAPHY
Gary Van Schooneveld, President of CT Associates, Inc., is an authority in nano-scale particle detection and contamination control for semiconductor manufacturing with over 35 years of specialized experience. He holds BS and MS degrees in Materials Engineering from Rensselaer Polytechnic Institute and an MBA from the University of Texas at Arlington.
He serves as Co-chair of the IRDS Critical Components Task Force and Co-chair of the SEMI Ultrapure Water Task Force, directing industry-wide contamination control standards development. His contributions have earned the SEMI Leadership Award (2024) and Advance Nanocontamination Measurement Service Award (2025). Gary has authored over 60 technical papers and presentations.