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Comparison of Optical Particle Sensors Used to Measure Particle Concentrations in High-Purity Chemicals: Phase II – Sensor Comparison in Chemicals

Authors

Debra Carrieri, FSI International
Donald C. Grant and Wayne Kelly, CT Associates, Inc.

Abstract

Optical particle sensors are used to measure particle concentrations in high-purity chemicals. The sensors are typically calibrated with polystyrene latex (PSL) spheres. Because the sensors have different optical configurations, their responses to naturally occurring particles in process chemicals vary widely. The specifications for particulate contamination set by the Semiconductor Industry Association do not describe the type of sensor optics that should be used when measuring particle concentrations. The develop- ment of more-meaningful standards requires a better understanding of the optical properties of chemicals and particles and their effects on sensor measurement. This study compares the responses of four commercially available sensors when counting naturally occurring particles in process chemicals.

CTA Publication #34: Presented at SEMICON West, July 1999

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