Nanometrology of Si Nanostructures Embedded in SiO₂using Scanning Electron Microscopy

A novel scanning electron microscopy for the imaging of embedded nanostructures is proposed. The Si nanostructures embedded in SiO 2 are clearly observed as bright contrasts at 30 kV electrons in the secondary electron mode. It is confirmed that the surface charging effect of SiO 2 on an SOI substrate is modified by the existence of an embedded Si structure. The edge of the embedded structure creates a yield peak in the secondary electron profile. The comparison of the transmission electron microscopy (TEM) image and the scanning electron microscopy (SEM) image indicates that the peak position represents the edge position of the embedded structure with nano-order precision. The metrological method using this imaging technique is successfully applicable to the width measurement of sub-10-nm embedded Si structures.