Nouvelles fonctionnalités de l’interface silicium/diélectrique pour la microélectronique

Abstract : Deposition of high-K oxides on silicon unavoidably results in the presence of an interfacial SiO2 layer. In order to remedy to this problem, a covalently grafted organic monolayer on silicon could be used as an ultrathin buffer layer between silicon and the oxide layer, thus avoiding the formation of a SiO2 layer. This work demonstrates, in a first part, that mixed carboxyl-terminated/methyl-terminated alkyl monolayers can be obtained in one step on Si(111)-H via photochemical hydrosilylation of undecylenic acid and decene mixtures. The compositional surface chemistry was determined from a quantitative IR study. Results prove that neither surface oxidation nor grafting through the carboxyl end group occurs. Careful analysis reveals that the mixed monolayers are richer in acid chains than the grafting solution, probably due to a strong physisorption of the acid on surface. Then, the thermal stability of monolayers has been analyzed in order to know whether they can withstand the temperatures used for oxide deposition. This was investigated by quantitative in situ infrared spectroscopy. Alkyl layers are thermally stable up to 250°C. In the range 250-300°C, alkene desorption occurs, accompanied with silicon oxidation. Desorption temperature is not significantly affected by changing the chain length from C18 to C6, but very short chains (C2, C1) are more stable. Acid-terminated layers remain intact up to 150°C. Above this temperature, acid groups are transformed into anhydrides. At 350°C, functional substituents are totally decomposed, though very few –CH groups have disappeared. This is explained by chain pairing on the surface, improving thermal stability of the layers.
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Anne Faucheux. Nouvelles fonctionnalités de l’interface silicium/diélectrique pour la microélectronique. Matériaux. Ecole polytechnique X, 2005. Français. ⟨tel-01259821⟩

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