Monosphere ion exchange resins have been gaining a wider acceptance in the production of ultrapure water (UPW) for use by the semiconductor industry. Ionic leakage is measurably lower from UPS resins when compared to conventional resins with a typical Gaussian particle size distribution. These UPS resins also offer significant improvements in resistivity profiles as well as low levels of total organic carbon (TOC) contaminants. For example, in UPS mixed beds it has been shown that an effluent resistivity of 18.2 megohm.cm is attainable after only 2 bed volumes of rinse water, and ∆TOC concentrations as low as 2 ppb have been achieved after rinsing for less than one hour.
These and other benefits associated with UPS resins in this application will be discussed. Complete separation of the anion and cation exchange resins in a mixed bed is necessary prior to regeneration to reduce or eliminate cross-contamination which will affect the amount of ionic leakage during the subsequent operating cycle. Calculations that predict sodium and chloride leakages based on the amount of resin remaining in the exhausted form after a regeneration (i.e., the degree of cross-contamination) will be presented. Ionic contamination and its relationship to the specifications for final ultrapure water quality will also be reviewed.