First Results from a New Online Nano Liquid Particle Monitor on Ultra-Pure Water

This paper presents initial results from new nano liquid particle monitoring technology for evaluating ultrapure water (UPW), which addresses a critical need in the industry to measure concentrations of colloidal particles below ~30 nm. The system combines UPW aerosolization/drying and water-based condensation particle counting to detect colloidal particles above a threshold size, ~10 nm in this work, while largely excluding much smaller residue particles arising from dissolved content. Results from extended use on two UPW systems, including one at a major semiconductor manufacturing foundry, demonstrate key performance attributes needed for a successful online monitoring system. These include clear settling to baseline, matched performance of multiple units in parallel, ability to distinguish between water qualities at different points in a polish process, long-term stability over multiple weeks of continuous use, ability to monitor the gradual rinse-down of replacement ion exchange resins in mixed beds, and the sensitive detection of breakthrough. Linear response to relevant nanoparticle concentrations is demonstrated by injections of different dilutions of monodispersed colloidal silica ranging from ~10 to ~60 nm diameter.