Historically, dielectric material used for silicon technology in the field of micro electronic is SiO₂. This is mainly due to the quality of the Si/SiO₂ interface as well as the easiness to perform and control the thickness of such films. However, the limits encountered in the miniaturization of transistors come now from the gate oxide. Combination of the low dielectric properties of SiO₂ and the requirements of thickness induces non negligible leakage current. Thus, SiO₂ is no longer adapted to the next generations of transistors and new dielectric materials are tested, such as metallic oxides (HfO₂, ZrO₂, TiO₂, Pr₂O₃, …) and also nitrides (Si₃N₄, AlN₃, …) and oxy-nitrides (Si-O-N, ....).

In this field, our goal is to test the capability of mixed oxide layers such as silicate ones in order to combine the advantages of the natural Si/SiO₂ interface and high dielectric constant of metal oxides. The materials we point out are barium silicates, mainly because of the good dielectric properties of BaO (ε_r(BaO) = 34). The first step of this work plays with high reactivity of barium towards metal oxides. It consists in studying the Ba/O/Si system in order to determine the optimal conditions for barium silicate elaborations. The elaboration technique consists in the incorporation of barium in silicon oxide film through a deposition step in UHV followed by an annealing and/or an oxygen exposure.

After barium deposition, first results were obtained in-situ by XPS and AR-XPS. They revealed the presence of barium carbonate. After annealing, barium carbonate is decomposed and lets place to the formation of barium silicate. Further analysis were carried ex-situ by TEM and SIMS and they confirmed the formation of the silicate. Finally, the presence of different morphologies (depending on the presence, or not, of initial SiO₂), revealed by AFM, will also be discussed.

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