Resistance and structural stabilities of epitaxial CoSi 2 films on (001) Si substrates
The resistance and structural stabilities of the epitaxial CoSi 2 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 CoSi 2 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 CoSi 2 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 CoSi 2 film. This has been accomplished by chemical etching using the standard buffered oxide etch solution. In the present experiment, as-grown epitaxial CoSi 2 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 CoSi 2 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 CoSi 2 films, as well as for the unacceptable quality of the polycrystalline silicide films, have been discussed.
Hsia, SL; Tan, TY; Smith, P; McGuire, GE
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