Analysis of low metallic contamination on silicon wafer surfaces by VPT-TXRF - quantification of 109 atoms/cm2 level contamination

Total reflection X-ray fluorescence (TXRF) spectroscopy is well known as on-line monitoring system for ULSI manufacturing line, but it is not useful for quantifying less than 10¹⁰ atoms/cm² metallic contamination because of its insufficient sensitivity. We developed a practical method named "VPT-TXRF" using vapor phase treatment (VPT) for quantifying metallic contaminants as low as 10⁹ atoms/cm² on silicon wafer surface with TXRF system. One important aspect of this method is that high sensitivity was achieved within a practical measuring time of 500 seconds while maintaining the original surface conditions of the wafers. We are convinced that this method will become the most useful monitoring method for critical process contamination of the coming ULSI manufacturing line.