Understanding Particle Contribution from Components Used in Ultrapure Water and High-Purity Chemical Systems and Their Impact on Industry-Driven Particle Requirements.
Gary Van Schooneveld – CT Associates, Inc
Bob McIntosh – Enviro-Energy Solutions
Managing contamination in ultrapure water (UPW) and chemical systems is of critical importance to maintain a robust manufacturing process resulting in high product yield in the semiconductor manufacturing process. Acceptable levels of particles in production, and consequently, allowable limits of these and other contaminants in UPW and process chemicals continue to be reduced in the International Roadmap for Devices and Systems (IRDS) in anticipation of advanced devices with smaller dimensions and increasingly complex three-dimensional structures. In order to help the industry respond to these needs, a number of SEMI specifications are being developed and revised with new methods, recommendations and performance requirements. Of particular interest to this paper is SEMI F104, Particle Test Method Guide for Evaluation of Components Used in Ultrapure Water and Liquid Chemical Distribution System. Aligning this SEMI document with the UPW and chemical quality needs provided within the IRDS roadmap will help the industry meet these challenging objectives.
In the area of particle contamination, the IRDS has provided guidance in the Yield section concerning the size and concentration of particles in order to successfully manufacture the next generation of devices. For example, for 2019, the critical size for non-electrically active particles is 7nm while for electrically active particles, the size drops to 3.5 nm. At this time, there is no widely accepted particle counting metrology that can measure these particles in-situ with sufficiently low background. To address this current limitation, the IRDS has moved to a “pro-active” particle approach specifying the maximum number of particles allowable in the feed to the final filters at sizes detectable by widely-deployed optical particle counters (OPCs). This philosophy is predicated on the removal efficiency of the final filter and the “Power Law” to translate the pre-filter measurement to the post filter particle population. For 2019, the IRDS guidance is 220 particles per liter ≥ 50 nm. In 2022, this level will drop to 140 particle per liter ≥ 50 nm
In order to establish appropriate particle criteria for SEMI F104, an extensive particle shedding study was conducted on valves, tubing and regulators from multiple supplies produced from a variety of raw materials using multiple OPC’s. In addition, models of typical UPW and chemical dispense systems were prepared. Particle rinse and steady-state shedding requirements were calculated based on the criteria established in the IRDS roadmap. The results of the particle shedding study were then compared the model to determine if the components tested would comply with the model requirements. Based on these analyses, the test method and performance requirements are being updated in the new release of SEMI F104.
This project was a highly collaborative industry effort with multiple companies providing materials and funding.
CTA publication #138: Ultrapure Micro 2019, Phoenix, AZ 2019