Detection of processes inducing profile changes of relief structures in SEM by analysis of their distorted images

摘要

A scan of trapezoidal protrusions by an electron beam was carried out in a SEM during an hour. This allows detecting some laws of a profile change due to contamination. The detection is based on analysis of distorted protrusion images obtained by the SEM. The greatest distortion of protrusion images was discovered around a scanned area. This distortion is not uniformed in the area (and associated with a non-uniform profile change in that area) that leads to a pitch change of a periodic structure. The protrusion image change in the scanned area is minimal, contrary to perceptible structure profile changes in that area. The latest circumstance allows defining geometrical parameters of a protrusion using a model developed for measurement of these parameters for a non-distorted structure. It was discovered that contamination process of periodic linear structures beyond the scanned area differs from the corresponding process for a flat surface. The difference firstly is due to dissimilar contribution of a volume and surface diffusion of hydrocarbon particles (HCP) that induce the contamination into various structure areas. Secondly it is due to different diffusion velocity of surface HCPs that are moving along and across of stripes with trapezoidal profile and over surfaces with different crystallographic indexes.