Arsenic diffusion and segregation behavior at the interface of epitaxial CoSi2 film and Si substrate
Arsenic diffusion and segregation properties at the interface of the epitaxial CoSi2 and Si substrate have been studied. Samples have been prepared using Co-Ti bimetallic source materials and two types of (001) Si substrates: n+ (doped by As to approx.2×1019 cm-3) and p. For the n+ Si cases, the lower limit of the CoSi2 film formation temperature is increased by approx.200°C to approx.700°C. SIMS results showed As segregation into Si. For epitaxial CoSi2 film formation at 900°C, the As concentration has increased by a factor of approx.2 within a distance of approx.30nm from the interface, while the incorporated As in the film is approx.30-50 times less than that in Si. For p-type Si substrate cases, the epitaxial CoSi2 film was first grown and followed by As+ implantation (into the film) and drive-in processes. It is observed that As was segregated to the CoSi2Si interface and diffused into Si. This is in qualitative agreement with our results obtained from the n+ substrate experiments and the results of other authors involving the use of polycrystalline CoSi2 films. In the present cases, all implanted As were conserved at a drive in-temperature of 1000°C for up to 100 s. This is in contrast to the polycrystalline CoSi2 film results which involve a substantial As loss to the film free surfaces. The physical reasons of this difference have been discussed.
