Direct Analysis of Metallic Contamination on Si Wafer Surface, Edge and Bevel Apex by LA-GED-MSAG-ICP-MS

The new laser ablation technique has been developed for a mapping analysis of metallic impurities on Si wafer surface, edge and bevel apex. Particles generated by a femto-second laser ablation were aspirated by an ejector and introduced to an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) via a Gas Exchange Device (GED) and analyzed. A Metal Standard Aerosol Generation (MSAG) was used for quantitation of metallic impurities in Si wafers. For analysis of Si wafer surface, a 300 mm wafer was placed horizontally on an X-Y-Z-θ-A ablation stage that moved to one spot to the other. The size of one spot was 10 mm x 10 mm, and the laser beam was scanned over the spot using a galvanometer mirror while the stage was fixed. For analysis of wafer edge, the laser beam ablated a 1 mm width using the galvanometer mirror while rotating the wafer by the ablation stage. For analysis of bevel apex, the wafer was tilted 90 degrees and rotated while the laser beam was scanned with a width of 0.3 mm using the galvanometer mirror. The surface mapping results clearly showed different contamination spots depending on the elements, and the bevel apex showed particularly higher contamination area.