A Raman spectrophotometric investigation of the phases formed during the cobalt silicidation by rapid thermal anneal

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Abstract
Raman spectrophotometry was used to determine the various phases of cobalt silicide formed during rapid thermal annealing of cobalt films deposited onto silicon (100) substrates. The samples were prepared by depositing a 600 ÅR cobalt film and then letting the reaction occur in a nitrogen ambient. Annealing was done for 20 s at temperatures ranging from 200 to 1000°C. The unreacted cobalt film was removed from the surface for the Raman spectrophotometric study. The initial phase, characterized as Co 2 Si, formed at 250°C. Two subsequent phases, CoSi and CoSi 2 , were identified as forming at 300 and 500°C, respectively. The corresponding three Raman peaks appeared at 204, 306 and 515.3 Δcm −1 , respectively. These peaks appeared and disappeared in accordance with the phase change in the film. The co‐existence of the two initial phases, Co 2 Si and CoSi, at temperatures near 300°C was also evidenced by Raman spectrophtometry. The Raman data correlated well with Auger electron spectroscopic depth profiles.