Structural and electrical characteristics of epitaxial CoSi₂ grown on n-Si_0.83Ge_0.17/n-Si(001) by reactive chemical vapor deposition using a Si capping layer

Epitaxial cobalt disilicide (CoSi₂) layers are grown on n-Si_0.83Ge_0.17/n-Si(001) using a sacrificial Si capping layer at the growth temperature T_s=650 °C by reactive chemical vapor deposition using cyclopentadienyl dicarbonyl cobalt (Co(η⁵- C₅H₅)(CO)₂). Structural and electrical properties of epi-CoSi₂/Si_0.83Ge_0.17/Si(001) were measured by transmission electron microscopy, X-ray diffraction, Auger electron spectroscopy and sheet resistance measurement as a function of annealing temperature. The combined results showed that the epitaxial CoSi ₂ phase by the reaction of Co with the Si capping layer was formed in the as-grown layers. Rapid thermal anneals for the investigation of thermal stability of the as-grown layers showed good thermal stability of the epitaxial CoSi₂ layers with the low sheet resistance value as low as ≅4.4 Ω/cm up to the annealing temperature as high as 850 °C without the formation of other cobalt silicide phases. At T_A=900 °C, Co ₂Si and CoSi phases with higher resistivity were formed due to the reaction of remaining Co on the surface with the diffusing Si or Ge from the SiGe layer and as a result the increase in the sheet resistance value to ≅26.6 Ω/cm was observed.