The straightforward fabrication of thin silicide layers at low temperatures by employing the molecular-incident reaction effect

Abstract

Because of the ease of formation, and good lattice match with Si, metal silicides often form high-quality epitaxial layers and have established themselves over the years as important technological materials with industrial applications. For the fabrication of silicon-based devices, the contact between metal electrodes and Si is a key issue. The properties of thin films on silicon substrates are strongly dependent on their microstructure and local chemistry. However, a concrete understanding of the influence of a silver layer on different transition metal/silicon interfaces is not currently available. We propose, for the first time, a new model called molecular-incident reaction effect (MoIRE) model that successfully explains the different chemical reactions for Co/Si and Ni/Si interfaces by the introduction of a 3×3R30o-Ag layer. The interaction transfer of silicon atoms forms a Co silicide for Co/3×3R30o-Ag/Si(111) with a thickness of a few nanometers, thus greatly reducing the temperature needed for the formation of a layered CoSi2 silicide compared to that for typical CoSi2 silicide formation at a Co/Si interface. Based on the MoIRE mechanism, the introduction of the 3×3R30o-Ag layer as an intermediate layer permits the silicidation temperature needed to produce a NiSi layer to be reduced to 400 K from typically above 600 K. This approach is advantageous for the formation of a silicide at the Ni/Si interface at low temperature. Based on the MoIRE model for silicide formation at Ni/3×3R30o-Ag/Si(111), we propose a technique for the synthesis Ni silicide layers at lower temperatures with simpler fabrication steps due to the difference in the properties between Co and Ni. This mechanism of low-temperature fabrication includes the formation of (1) a 3×3R30o-Ag and (2) a NiSi layer. The findings presented herein will be useful for more efficiently forming salicides in integrated circuit fabrication, as well as for developing superconducting circuits and quantum bits for quantum computing.