Molecular dynamics investigation of silicide technology formation

Abstract

Physical and chemical properties of ultrathin suicide films are of considerable interest because of their reduced coordination and symmetry lead to important changes in crystallographic and electronic structure with respect to the same material in the bulk. These suicides are characterized by a very low Schottky barrier to n-type Si combined with a small electrical resistivity and are therefore, attractive for Si based technology '.Since interface with Si is buried by an overlayer and its structure depends on the materials and conditions during formation, it is difficult to clarify atomic structure of the interface. Hence, it is important to know the atom arrangement at the metal-silicon region in order to clarify the electronic structure of real interfaces. The formation of silicide films on silicon is accompanied by atom adsorption on surface, metal atom diffusion into silicon lattice, forming and diffusion of point defects which are taken into account in all above mechanisms. For example, the formation of Pd2Si on silicon generates point defects, which diffuse into silicon substrate and promote the diffusion of buried dopant layers. Peculiarity of this process is characterized by asymmetric diffusion of buried marker layers and surprisingly low diffusion process temperature (near 200°C). Buried marker layers move toward the silicon surface. This anomaly is explained as the result of silicidation process. The similar diffusion phenomena (asymmetric diffusion of buried Sb-doped p-n-p-junctions) occured during Co and Ti silicide formation. These low-scale effects may be adequately investigated by means of molecular dynamics (MD) method. Here we present some of preliminary results of low-energy silicide formation technology simulation carried out by this method