Ellipsometric Study of Ion-Implantation Damage in Single-Crystal Silicon - An Advanced Optical Model

摘要

Damage depth profiles were characterized by spectroscopic ellipsometry using an improved optical model. The results were cross-checked by backscattering spectrometry. Different ion species and doses were applied to create damage profiles of different depth-, width-, and height-parameters. Our previously developed optical model consists of a stack of homogeneous layers: a native oxide layer at the surface, a thin amorphous layer, and 10-100 layers, depending on the depth resolution, with fixed and equal thicknesses, and damage levels described by a coupled half-Gaussian depth profile function. In the improved optical model the damage profile is described by sublayers with thicknesses inversely proportional to the slope of the profile. The complex refractive index of each sublayer is calculated by the Bruggeman-effective medium approximation using the complex dielectric function of the single-crystalline silicon and the implanted amorphous silicon as layer components. The thicknesses of the sublayers are automatically calculated from the four parameters of the coupled half-Gaussian profile, while the number of the layers are held constant. This ensures that the calculation time does not increase, when using the improved model. The improved fit quality and the results of backscattering spectrometry basically supported the new optical model.