On-Line Metal Concentration Measurement at an Ultra-Trace Level in DIW by Solid Phase Extraction Method Coupled with ICP-MS

Abstract

Metal contamination is a critical issue in semiconductor manufacturing processes, where controlling the concentration of metals in the deionized water (DIW) used for wafer rinsing and chemical dilution is necessary. In our previous study, we reported an ultra-trace level measurement method using solid-phase extraction (SPE) with a monolithic resin and inductively coupled plasma mass spectrometry (ICP-MS). However, this method had limitations regarding rapid metal concentration confirmation and contamination risks due to manual processing and sample delivery. This study proposes an on-line metal measurement system that uses an automated SPE technique coupled with ICP-MS to address the shortcomings of the conventional method. The system provides continuous on-site monitoring of ultra-trace metal concentrations in DIW, reducing preconcentration volume by up to 60% compared to the conventional method owing to minimizing contamination by automating all processes. Moreover, the system achieved reliable results similar to the conventional method, high analytical stability, with the relative standard deviations (RSDs) within 5% for a concentration of around 0.05 ng/L (n=4) using a test solution. We also evaluated the metal removal filter as an application of the system mentioned above, simultaneously analyzing multiple elements at the single-pg/L level and confirming the performance of the filter.