Surface Inspection of Silicon-on-Insulator Wafers with Ultra Thin Top-Si Layer by Laser Scattering

Abstract

This paper discusses an investigation into the abilities to detect light point defects on a silicon-on-insulator (SOI) wafer surface by inspecting both the haze and the scattering intensity of the poly styrene latex (PSL) spheres on a SOI wafer with a top-Si layer thinner than 120 nm. It is found that a SOI wafer with a top-Si layer thickness exhibiting a lower reflectance at the wavelength used in scanning the surface results in a higher haze and weaker scattering intensity for PSL spheres. Although each size of PSL spheres has its own thickness of its top-Si layer with its lowest scattering intensity. The electric field distributions above the SOI wafer surface with various top-Si thicknesses are calculated to evaluate the potential for scattering the incident light at various wavelengths by the surface particles. It is predicted that p-polarized light with wavelengths between 290 and 370 nm is most suitable for inspecting SOI wafers with a top-Si layer thickness below 120 nm.