Schottky-barrier height and electronic structure of the Si interface with metal silicides: CoSi2, NiSi2, and YSi2.

Abstract

Using the linear muffin-tin orbitals in the atomic-sphere approximation with the local-density approximation (LDA), we studied the electronic structure and Schottky-barrier height (SBH) of the Si interface with metal silicides: ${\mathrm{CoSi}}_{2}$, ${\mathrm{NiSi}}_{2}$, and ${\mathrm{YSi}}_{2}$. We used large supercells with 9 ${\mathrm{Si}}_{2}$ and 8--10 silicide (${\mathrm{CoSi}}_{2}$, ${\mathrm{YSi}}_{2}$) layers for the (111) interface and with 11 ${\mathrm{Si}}_{2}$ and 11 silicide (${\mathrm{NiSi}}_{2}$, ${\mathrm{CoSi}}_{2}$) layers for the (001) interface. Together with our previous calculations on the two types of ${\mathrm{NiSi}}_{2}$/Si(111) interfaces, we demonstrate that the LDA calculation with a large supercell correctly reproduces the dependence of experimental SBH's on the interface structure and type of metal silicide. Electron transfer at the silicide-Si interface depends significantly on the atomic structure of the interface, especially the interfacial space, whether atoms are crowded or not. The energy distribution of interfacial gap states varies significantly with interface atomic structures. These electronic structures directly depend on the interface atomic structure; in contrast the calculated SBH's do not always depend on the interface structure. We discuss the underlying mechanisms for the formation of Schottky barriers.