Probing Co/Si Interface by Raman Spectroscopy

The characteristics of the metal on the Si surface have been extensively explored due to the industrial relevance of transition metal silicide in integrated circuit technology and scientific interest in the influence of the adlayer on Si substrate reconstruction and heterodiffusion. Even though the interaction of Co with Si is not entirely understood, there are still disagreements over the nature of the Co/Si system. Several problems remain unsolved, including predictions of the phase that would precipitate among the several phases of the Co/Si system as a function of film thickness and temperature. Therefore, in order to understand the same, cobalt (Co) thin films of thicknesses 10, 40, and 100 nm were produced by electron beam physical vapor on silicon substrates. After deposition, the samples were further annealed at 200, 300, and 400 °C for 2 h. Micro-Raman spectroscopy (due to its non-destructive nature) was used to analyze the chemical composition and silicide formation at the interface as a result of the thickness and temperature variation in as-deposited and annealed samples. The results demonstrate that the grown films are of high quality and devoid of impurities. Studies reveal that silicide is formed during deposition at the interface, and the development of a new band at 1550 cm – 1 as a result of annealing shows structural transformation from CoSi to CoSi2, which strengthens further at higher annealing temperatures.