Abstract:

INDUSTRY CHALLENGE
Particle precursors (PPs) defined as medium to high-molecular weight organics that can form particles on the wafer surface during drying — remain a concern for the semiconductor industry. Potential sources include high surface area components such as ion exchange resin, filters, membrane contactors, and polymer piping.

Prior IRDS Critical Components Task Force work has demonstrated the potential for correlating PP concentration, measured via SEMI F121-validated metrology, to on-wafer particle defects. The next step is to establish a standard test method for assessing defectivity risk from various PP sources — providing suppliers with a tool to improve products and proactively manage yield risk.

APPROACH AND METHODOLOGY
This experimental study follows from a 2024 IRDS Critical Components Task Force investigation of PP contamination extracted from PFA and PVDF piping and its contribution to on-wafer particle formation. The current phase evaluates repeatability and sensitivity of the test method using three PFA tubing types and three PVDF piping types. One PFA and one PVDF sample serve as replicates to validate variability; additional samples assess method sensitivity.

Three wafer surfaces — prime silicon, thermal oxide, and silicon nitride — are used to assess the influence of surface chemistry on particle formation and adhesion. Extracts are prepared at 85°C in ultrapure water (UPW) for 14 days, then characterized by Liquid Nanoparticle Sizing (LNS) and spin-coated onto 100 mm wafers. On-wafer particle concentrations are measured by Surface Enhanced Particle Sizing (SEPS) using a UNISERS tool and correlated to LNS data to derive defectivity risk coefficients.

ADVANCEMENT OVER PRIOR RESEARCH
This work extends a 2024 IRDS Critical Components Task Force study in which combined PFA and PVDF extracts in hot UPW revealed significant differences between the two materials in both PP extraction levels and on-wafer particle counts at equivalent liquid concentrations — results presented at the IRDS/SEMI session at UltraFacility 2024. The current study advances those findings by testing individual sources separately to assess repeatability and sensitivity, and by introducing multiple wafer surface chemistries as an additional variable.

KEY TAKEAWAYS
• Sources and risks of particle precursors in high-purity polymer piping systems.
• Quantitative PP extraction data from PFA and PVDF materials and components.
• How PP concentration in liquid extracts translates to on-wafer particle counts.
• The influence of wafer surface chemistry on particle formation and adhesion.