Modeling of light scattering by submicrometer spherical particles on silicon and oxidized silicon surfaces

We report angle resolved scattering characteristics of individual submicrometer polystyrene spheres on silicon and on a 91.5 nm thick film of oxide on silicon. Both these surfaces are considered optically smooth because the root mean square (rms) vertical roughness ? is much less than the wavelength ? (???). Scattering was measured as a function of polarization using a He-Ne and argon laser at varying degrees of incident angle. The experimental results are compared with a semi-analytical model of sphere/surface light scattering and a finiteelement time-domain electromagnetics code used in conjunction with a far-field extrapolator called EXTRMAP. The scattering measurements showed good to excellent agreement with both models. The semianalytical model could be improved by fully accounting for standing wave effects, a phenomenon the finite-element time-domain model inherently includes. The results are qualitatively explained with reference to both standing wave phenomena and the silicon surface reflectance, which varies significantly as the beam incident angle and polarization are changed.