Degradation of doped Si regions contacted with transition-metal silicides due to metal-dopant compound formation

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Abstract
The stability of doped Si with respect to a contacting silicide is investigated for TiSi2, VSi2, CoSi2, ZrSi2, MoSi2, TaSi2, WSi2, and PtSi on As- and B-doped Si by calculation of the critical portion of the ternary diagram. From the thermodynamic calculations it is shown that high B concentrations in Si will be unstable underneath an overlaying TiSi2, TaSi2, and ZrSi2 film. In the case of As-doped Si, high concentrations in Si are unstable with respect to an overlaying TiSi2, TaSi2, ZrSi2, and PtSi film. The effect of metal-dopant compound formation is not expected to occur in the case of VSi2, MoSi2, and CoSi2, and probably also not for WSi2, on B-doped Si. It is similarly not expected to occur in the case of VSi2, CoSi2, MoSi2, and WSi2 on As-doped Si. The relevance of these thermodynamic predictions for technological applications is illustrated by experimental results on the diffusion of B and As from various implanted silicide layers. From comparison of thermodynamic properties of M-P and M-As compounds, it was shown that no advantage is expected from P over As as far as metal-dopant compound formation is concerned.