MODELING OF LIGHT-SCATTERING BY SUBMICROMETER SPHERICAL-PARTICLES ON SILICON AND OXIDIZED SILICON SURFACES

We report angle resolved scattering characteristics of individual subm icrometer polystyrene spheres on silicon and on a 91.5 nm thick film o f oxide on silicon. Both these surfaces are considered optically smoot h because the root mean square (rms) vertical roughness sigma is much less than the wavelength lambda (sigma much less than lambda). Scatter ing 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 scat tering and a finite-element time-domain electromagnetics code used in conjunction with a far-field extrapolator called EXTRMAP. The scatteri ng measurements showed good to excellent agreement with both models. T he semianalytical model could be improved by fully accounting for stan ding wave effects, a phenomenon the finite-element time-domain model i nherently includes. The results are qualitatively explained with refer ence to both standing wave phenomena and the silicon surface reflectan ce, which varies significantly as the beam incident angle and polariza tion are changed. (C) 1996 Society of Photo-Optical Instrumentation En gineers.