The presence of trace contaminants in ultra-pure water (UPW) used in fabrication process can greatly affect the yield and quality of industrial products. In the present study, the electrodialytic enrichment of metal cations as a means of continuously monitoring the UPW quality was studied. A newly designed electrodialytic enrichment device (EED) was used to quantitatively transfer metal ions from samples to dilute nitric acid, which was then directly introduced into an inductively coupled plasma—mass spectrometry (ICP–MS) instrument. This process could be performed without contamination of the sample, and the enrichment factor was solely dependent on the flow rate ratio of the sample and acceptor solutions. The transference of analytes into the acidic solution improved the responsivity of the ICP–MS analysis, especially at low concentrations of less than 1 μg/L. Blank solutions to support the analysis of UPW could be produced using the EED effluent, from which metal ions were quantitatively removed. In addition, calibration curves with concentration ranges of several nanograms per liter were obtained by preparing standards using a dynamic gravimetric method while employing a single bottle and continuous mass monitoring to avoid any contamination from the volumetric flasks. The sensitivities associated with the ICP–MS analysis of a number of trace metal ions were improved by one or two orders of magnitude. The data show that the present EED is able to continuously produce enriched analyte solutions to allow the ongoing monitoring of UPW quality.

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In the production of semiconductors, ultrapure water is used for cleaning in each process. In recent years, the adverse effects of impurities in ultrapure water for cleaning have increased with the miniaturization and high integration of the circuit-line width of semiconductors. Therefore the demand for high-quality ultrapure water has increased. We examined the metal adhesion restraint on silicon wafers based on the adsorption of polystyrene sulfonate (PSA) and metal ions. PSA was microinjected into a sample of ultrapure water containing the metal, and a cleaning vessel was allowed to overflow with the sample. Subsequently, the wafers in the sample were immersed and the amount of the metal deposited on them was measured. In addition sulfur concentration was calculated. It was found that the adhesion of the metal ions adsorbed with PSA in ultrapure water on the wafers is suppressed. A metal adhesion restraint rate greater than 95% was obtained with the polyvalent metal ions. Furthermore, it was revealed that the adhesion of PSA to the wafer was negligible. We may apply this technique as a metal contamination restraint method for each cleaning process in the production of semiconductors.