X-ray reflectivity studies of very thin films of silicon oxide and silicon oxide-silicon nitride stacked structures

Oxide/nitride/oxide films were deposited onto bare silicon substrates by low-pressure chemical vapor deposition (LPCVD) of silicon nitride and thermal oxidation. The X-ray reflectivity technique has been used to study the influence of the growth conditions and of different cleaning procedures of the silicon substrate on the structure and morphology of the deposited multilayers. The results revealed how, from an analysis of the X-ray reflectivity data performed by using Fresnel equations for multilayers modified to account for the interface imperfections, we determine, in a nondestructive manner, structural parameters such as density, thickness, roughness, and interface structure of the whole dielectric layers, giving us more information and greater sensitivity respect to cross-section transmission electron microscopy (TEM) and ellipsometric measurements. (C) 2001 Elsevier Science B.V. All rights reserved.