Should We Analyze for Trace Metal Contamination at the Edge, Bevel, and Edge Exclusion of Wafers?

The edge, bevel, and edge exclusion area of a wafer has historically been difficult to monitor for trace metals. Standard trace metal surface techniques such as total reflection x-ray fluorescence spectroscopy, time-of-flight secondary ion mass spectrometry, and vapor phase decomposition inductively coupled plasma are currently not capable or have difficulty measuring metals to the edge and bevel of the wafer. With shared metrology toolsets and new materials being introduced into semiconductor fabs, it is important to measure possible contamination in these areas of the wafer. Tools that have edge grip pins or centering and aligning pins, also are at risk to contaminate wafers at the edge and bevel. A technique had been developed known as the beveled edge analysis tool that chemically extracts contamination from the edge, bevel and edge exclusion of a wafer that is then quantified by inductively coupled plasma mass spectrometry. In this study we will show correlation of this technique to standard trace element analysis methods. We will also present data from characterizing processes and fab tools that will benefit from this measurement.