Resistance and structural stabilities of epitaxial CoSi2 films on (001) Si substrates

Abstract

The resistance and structural stabilities of the epitaxial CoSi2 films, grown on (001) Si substrates using sequentially deposited Ti-Co bimetallic layer source materials, have been investigated by further anneals under extended conditions. In contrast to reported polycrystalline silicide film cases, the epitaxial CoSi2 films are very stable under the additional rapid thermal annealing treatment at 1100 °C for times from 10 to 60 s. This means that such CoSi2 films are able to stand the further heat treatment required in the ultralarge-scale integration regime of Si integrated circuit fabrication. The quality of the further annealed films has been actually improved: The film resistivity has decreased to reach a value as low as 10 μΩ cm, and the film structure has become more perfect, e.g., the densities of antiphase domains and film-Si interface facets have been decreased. For technological applications, it is necessary to remove the Ti-Co-Si alloy layer formed concomitantly on top of the as-grown CoSi2 film. This has been accomplished by chemical etching using the standard buffered oxide etch solution. In the present experiment, as-grown epitaxial CoSi2 films with and without the Ti-Co-Si alloy top layers have been both included and the same film resistance and structural stabilities have been observed. Thus, the excellent resistance and structural thermal stabilities of the present CoSi2 films result from the single-crystal nature of the films and not the effect of the top Ti-Co-Si capping layer. Mechanisms responsible for the excellent quality of the epitaxial CoSi2 films, as well as for the unacceptable quality of the polycrystalline silicide films, have been discussed.