Morphology of TiSi₂ and ZrSi₂ on Si(100) and (111) surfaces

Abstract

The morphologies of ZrSi₂ on Si(111) and TiSi₂ on Si(111) and (100) have been investigated, and the results compared and contrasted. Films were prepared by UHV deposition of Ti or Zr onto clean, reconstructed Si(100) or (111) substrates, and reacted by in situ annealing. The sheet resistivity of the ZrSi₂ was measured and found to be 33-42 μΩ-cm. The morphologies were examined by transmission and scanning electron microscopy. In particular, the islanding properties were studied; both the temperature of the onset of islanding and the island characteristics were measured. The surface and interface energies have been determined from the contact angles of the silicide islands, according to a solid-state capillarity model. The system of ZrSi₂ on Si(111) was found to have surface and interface energies lower than those of the system of TiSi₂ on Si(100), but higher than those of the system TiSi₂ on Si(111). ZrSi₂ on Si(111) was found to island at a higher temperature than TiSi₂ on either substrate, a result attributed to kinetic effects. Areal coverage of the islands was measured, and the results were consistent with the solid-state capillarity model. For both TiSi₂ and ZrSi₂, increasing faceted structure was observed with increasing anneal temperature. Preferred faceting planes were found to be of Si(111) and (100) type for TiSi₂ islands and of Si(111) type for ZrSi₂. Faceted islands were apparently epitaxial. As the solid-state capillarity model does not directly apply to islands with a faceted structure, an observation of the percentage of faceted islands produced by different annealing temperatures was used to suggest the processing conditions in which the model is applicable.