Interface reaction of a silicon substrate and lanthanum oxide films deposited by metalorganic chemical vapor deposition

The interfacial layer and the transition layer of the lanthanum oxide film on a Si substrate prepared by metalorganic chemical vapor deposition have been studied by X-ray photoelectron spectroscopy, cross-sectional scanning transmission electron microscopy, and energy dispersive X-ray analysis. It was revealed that the diffusion of silicon into the lanthanum oxide occurs during the film deposition and post-annealing, and consequently, a lanthanum silicate is formed. The composition of lanthanum and silicon in the silicate is nonstoichiometric and gradually changes in the direction of the film thickness. These results show that the suppression of the silicon diffusion is essential in controling the properties of the dielectric films.