Roughness improvement of the CoSi2/Si-interface for an application as buried silicide

The material CoSi2 is preferred for the fabrication of buried silicide films between silicon device layer and buried oxide of SOI substrates for BICMOS integrations. Such an application needs excellent quality of the interface between the silicide and the silicon device layer. Using the conventional cobalt salicide process the roughness and waviness of the interface is too large for a device application. In this presentation three technologies to improve the CoSi2/Si-interface quality were characterized. Using the first technology a very thin single crystalline CoSi2 film was fabricated on a silicon substrate. This film acts as initial layer to produce thicker single crystalline silicide films. By the second technology an interlayer between cobalt and the silicon substrate was used to mediate an epitaxial CoSi2 growth. Different types and materials were tested. Using the third technique a sacrificial layer of polycrystalline silicon between cobalt and the silicon substrate was consumed during the silicidation reaction. This method gives the best results with interface roughness values of less than 1 nm. The interface roughness was measured after CoSi2 removal using AFM. A possible epitaxial growth of the silicide films was investigated with XRD analysis. Cross sectional SEM images were prepared to analyze the interface waviness and the CoSi2 structure.