Evaluation of the Cleanliness of Ultrapure Water by the Analysis for Metal Concentration Depositted on Si Wafer Surface Using Vapor Phase Decomposition/Inductively Coupled Plasma Mass Spectrometry

Along with the shrinkage of LSI geometries, a higher quality of ultrapure water has been continuously required. Analytical technology for ultrapure water has also progressed before ultrapure water production technology improvements. In this study, we performed optimization of the analytical conditions for the direct analysis of acid droplets, and established an analytical technology for measurements of trace amounts of metallic impurities deposited on a wafer surface by means of Vapor Phase Decomposition (VPD)/Inductively Coupled Plasma Mass Spectrometry (ICP-MS). As a result, analytical technology for metallic elements of the 1 × 108 atoms/cm2 level on wafer surface has been established. By applying analytical technology to the wafer that has been contacted with ultrapure water, a new evaluation technology for ultrapure water quality by means of wafer surface contamination has been established. We confirmed good correlations between metal contamination of the wafer surface and the concentration in ultrapure water. This new quality evaluation technology is expected to contribute a further improvement of ultrapure water for future LSI manufacturing.