Light scatter from defects on chemically-mechanically polished wafers

Detection and reduction of defects on chemically-mechanically polished (CMP) wafers are important concerns in semiconductor manufacturing. The physical and light scattering characteristics of typical CMP wafer surface defects including roughness, dishing, particles, and scratches are investigated in this dissertation.; A new scatterometer is developed for the light scattering study. The system measured “true” bidirectional reflectance distribution functions (BRDF) and differential scattering cross sections (DSC) in plane of incidence. Through comparing experimental results with modeling and with expected values from standard samples, the system is proven to be able to deliver accurate scattering measurements on small features and wafer surfaces.; The physical characteristics of metal roughness, metal dishing, contaminants, and scratches on tungsten (W) and copper (Cu) CMP wafers are studied. The power spectral density of W and Cu, the metal dishing's dependency on linewidth and pattern density, the different compositions of various contaminants, and the appearances of scratches are investigated.; The scattering characteristics of the patterned W and Cu CMP wafer substrates are studied. A light scattering scheme which measures metal roughness on a patterned wafer is developed based on the Rayleigh-Rice vector perturbation theory. The dishing's dependency on pattern density is characterized using light scattering, and the scatter from Cu line-edges is measured and compared to the scatter from a step simulated using the Kirchhoff approximation method.; The angle-resolved scatter from individual 0.305 μm and 0.482 μm polystyrene latex spheres on blanket silicon (Si), silicon dioxide (SiO ₂) film, and W film surfaces is measured and the effects of roughness and a dielectric film on particle scatter are investigated. The scattering characteristics of diamond-tip scribed scratches on a filmed surface, which are long linear scratches and are about 0.8 μm wide and 90 nm deep, are studied as a function of incident angle and polarization. Finally, a light scattering scheme that classifies particles and scratches is developed using their different dependency of differential scattering cross sections on beam diameter.