Dresden 2006 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 9: Functional thin films II
DS 9.5: Vortrag
Dienstag, 28. März 2006, 12:15–12:30, GER 37
Titanium at the interface between Si and high-k silicates — •Jarek Dabrowski, Grzegorz Lupina, Gunther Lippert, Anil Mane, and Hans-Joachim Müssig — IHP, Im Technologiepark 25, 15236 Frankfurt(Oder), Germany
When a high-k film containing a high concentration of fast interface states is covered with a Ti overlayer and subsequently annealed, most of the fast states disappear. By analysing the behavior of Ti at SiO2/Si(001) interfaces as revealed by ab initio calculations, we discuss the mechanism of this effect. Passivation by substitution is excluded because a Ti atom substituting a Si atom with a dangling bond has similar electrically active states in the gap as a Si dangling bond. Moreover, the Ti atom would not stop at the interface to substitute the Si atom, but would advance into the substrate to form a seed of a metallic Ti silicide inclusion. We may also exclude that Ti dissolved in the film induces a recombination of interfacial dangling bonds indirectly, through strain field. This is because the recombination would require a long-range reconstruction of the oxidized Si, but the passivation occurs already at 200∘C. We argue that the electrically active interfacial defects passivated by Ti are valence-alternation defects associated with high compressive stress. Such defects are expected to appear in SiOx at the very interface because the oxidation of Si occurs in a constrained manner under the high-k film. Titanium atoms dissolved in the interfacial silicate layer expell Si atoms, while the metallic Ti overlayer drains oxygen from the defected interfacial sites. This results in Si regrowth in previously strained areas