The response of a wafer surface scanner is usually determined by means of calibration wafers carrying polystyrene latex (PSL) spheres. The responses of a scanner to real-world contaminant particles with a nonspherical particle shape and a different refractive index are generally not well-understood. In this paper, uniform-sized particles of Al, Al2 O3 Si, SiO2, Si3 N4 and Zn have been deposited onto bare silicon wafers for use as calibration standards to study the response of wafer surface scanners to nonspherical, real-world particles. The particles used were irregular in shape and covered a size range of 0.2 μm to 1.0 μm. The morphological characteristics of the particles have been examined by a scanning electron microscope (SEM). The experimental response of a commercially available wafer surface scanner (Tencor Surfscan-4000) to these uniform-sized, nonspherical particles has been determined. The experimentally determined response of the wafer surface scanner has been compared with theoretical calculations based on Mie scattering and Fresnel surface reflections.

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