Croissance de films minces de nitrure de bore hexagonal et cubique par dépôt chimique en phase vapeur assisté par plasma : caractérisations optiques et électriques

Abstract : The aim of this work was to synthesise cubic boron nitride thin films (c-BN) by chemical vapour deposition assisted by microwave plasma (2,45 GHZ), in order to carry out a device based on surface acoustic waves (SAW). We initially obtained the hexagonal phase (h-BN), analysed the deposition parameters ad the conditions of the growth which led to a good reproducibility of the layers. The growth c-BN thin films is very delicate and is generally obtained with physical vapour deposition methods (PVD). We succeeded in the fabrication of cubic phase (c-BN) by a chemical vapour deposition (CVD) method and we could elaborate this material successfully by applying an RF bias (13,56 MHz) to the substrates. The BN films were characterized by infrared (IRTF), MicroRaman (MRS), m-lines spectroscopies, as by electrical (I(V), C(V)) and physicochemical (XPS) methods. We developed a method of determination of the orientation of the optical axis "c" of the h-BN films by infrared spectroscopy, while working at oblique incidence. Indeed, with this technique is possible to excite the Lo modes due to the Berreman effect. This allowed us to extract a new "effect" dielectric function which takes into account the preferential orientation of crystallites. Using this method, we show that it is possible to modify the "c" axis orientation by changing the plasma power or the bias of the substrates. The synthesized films correspond to a mixture of h-BN and c-BN phases. The technique developed using IR allows us to show that the "c" axis of the h-BN sublayer is parallel to the substrate surface, allowing thus the growth of c-BN. These results were also corroborated by high resolution transmission electron microscopy measurements (HRTEM). As for PVD techniques, the two important parameters for the synthesis of the c-BN by PECVD are the energies and the magnitude of the incident flux of ions. In addition, electric analyses allowed us to put forward some properties of the BN as its rather large sensitivity to room moisture and its high resistivity, which should make it possible to determinate better precautions of use in the realization of microelectronic devices
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Ali Soltani. Croissance de films minces de nitrure de bore hexagonal et cubique par dépôt chimique en phase vapeur assisté par plasma : caractérisations optiques et électriques. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 2001. Français. ⟨NNT : 2001METZ034S⟩. ⟨tel-01748966⟩

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