Abstract:

Measurement of the sizes and concentrations of particles in colloidal suspensions has historically been a challenge, particularly for suspensions with particles smaller than 100 nanometers. A newly developed measurement device, a Liquid Nanoparticle Sizer (LNS), allows sizing and counting of particles as small as 5 nanometers in these suspensions.

The LNS consists of an ultrafine nebulizer and a scanning mobility particle sizer (SMPS). A colloidal suspension undergoing analysis is diluted on line in ultrapure water (UPW) and injected into the nebulizer. The nebulizer generates a droplet distribution in filtered air which is subsequently dried to form an aerosol containing the particles originally in the colloidal suspension. The size distribution (PSD) of the aerosol particles is measured using an SMPS capable of measuring particles as small as 5 nm in size.

This paper describes the LNS measurement technique in detail and shows examples of its use in measurement of particle size distributions in colloidal suspensions such as chemical/mechanical planarization (CMP) slurries and measurement of the retention of particles and macromolecules as small as 5 nanometers by microporous membrane filters and ultrafilters.