Analysis of Low Metallic Contamination on Silicon Wafer Surfaces by Vapor-Phase Treatment and Total Reflection X-ray Fluorescence Analysis

We have developed a new practical method for quantifying metallic contaminants with concentrations as low as 10 9 atoms/cm 2 on silicon wafer surfaces. It is named “VPT-TXRF” and uses vapor-phase treatment (VPT) with a total reflection X-ray fluorescence analysis (TXRF) system. VPT can change the form of metallic impurities on the surface from thin-film type to particulate type and thus the detected X-ray intensity is increased because of the inherent nature of TXRF, namely, the angular dependence of fluorescence yield. By this method, high sensitivity was achieved within a practical measuring time of 500 s, while maintaining the original surface contamination distribution of the wafers. We are convinced that this method will become the most useful monitoring method for the critical process contamination of the future ultra-large-scale-integration (ULSI) manufacturing line.