Abstract:

INDUSTRY CHALLENGE
Mixed Bed Ion Exchange (MBIX) resins are a critical component of ultrapure water (UPW) polishing systems. While designed to remove ions, all MBIX resins simultaneously shed metals, organics, particles, and particle precursors — and it is these shedding rates, not ion removal efficiency, that define product water quality and contamination risk to semiconductor yield. Comprehensive comparative characterization of commercially available MBIX resins using multi-parameter metrology beyond SEMI C93 has not been widely reported.

APPROACH AND METHODOLOGY
Five commercially available semiconductor-grade MBIX resins were evaluated using a standardized SEMI C93 test apparatus. The analytical program included both standard C93 methods (metals by ICP/MS, nanoparticle counting, and online TOC) and additional techniques: extended particle sizing down to 4 nm, on-wafer particle analysis by Sequential Spin Coating combined with Surface Enhanced Particle Sizing (SSC+SEPS), organic speciation by LC-OCD-OND, and qualitative residue characterization by FTIR-ATR. Results are compared to equivalent testing conducted in 2019.

RESULTS
Significant differences were observed across the five resins for all contamination categories. Metals showed the greatest variability, followed by organics and particles. Organic speciation revealed that amino acids and polystyrene sulfonate (PSS), both candidate particle precursors, are strongly correlated across all resins, consistent with ion-pair transport through the MBIX bed. These species account for a substantial fraction of the 1 ppb TOC target, with the remainder uncharacterized for most resins. On-wafer SSC+SEPS analysis was explored but limited by signal-to-noise at the contamination levels encountered.

KEY TAKEAWAYS
• No single resin leads across all parameters; metals are the primary differentiator, followed by TOC and particles.
• Cationic and anionic particle precursors co-elute as ion pairs — a finding consistent with prior work by Zazzera et al.
• Measurement techniques beyond SEMI C93 are needed to fully differentiate MBIX resin quality at levels relevant to advanced semiconductor manufacturing.