Investigation of the Composition of the Si/SiO 2 Interface in Oxide Precipitates and Oxide Layers on Silicon by STEM/EELS

We investigated thermal oxide layers of different thickness on (100) and (111) silicon substrates by STEM/EELS in order to determine the stoichiometry profiles and compared these with stoichiometry profiles of plate-like and octahedral oxide precipitates in silicon. The results of these investigations demonstrate that the stoichiometry of SiO 2 ( x =2) cannot be reached if the oxide layer thickness is lower than 10 nm for thermal oxides grown at 900 °C. The lower the thickness of the layer is the lower is the maximum x value. This is due to an interface layer of equal maximum slope for all oxide layers. The slope was obtained from fitting by sigmoid functions. Similar results were found for the oxide precipitates in silicon but the slope is somewhat lower.