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OTD News Light Scattering by Metallic Particles on Silicon Wafers Light scattering is used by semiconductor manufacturers to inspect silicon wafers for particulates, defects, and surface roughness. Since a particle’s size determines its potential to cause device failure, it is critical to be able to accurately measure particle size. Polystyrene latex (PSL) spheres are often used to calibrate wafer inspection systems, but these model particles do not behave like real-world particles. For example, they scatter much less light than metallic particles do. A system, calibrated using PSL spheres, might report that a harmless metallic particle is much larger than it really is, causing more wafers to be rejected than necessary. Validated theories for light scattering are necessary to avoid such problems. The Optical Technology Division, in collaboration with NIST's Building and Fire Research Laboratory and the University of Maryland, has developed a method for generating uniformly sized, pure copper particles and depositing them on silicon wafers. We performed measurements of the light scattered by these particles and found very good agreement with theoretical calculations. The code for these calculations has been made publicly available through the SCATMECH library of scattering codes. Online: September 2002 |