Atomic Diffusion in Cu/Si (111) and Cu/SiO₂/Si (111) Systems by Neutral Cluster Beam Deposition

The Cu films are deposited on two kinds of p-type Si (111) substrates by ionized cluster beam (ICB) technique. The interface reaction and atomic diffusion of Cu/Si (111) and Cu/SiO₂/Si (111) systems are studied at different
annealing temperatures by x-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Some significant results are obtained: For the Cu/Si (111) samples prepared by neutral clusters, the interdiffusion of Cu and Si atoms occurs when annealed at 230°C. The diffusion coefficients of the samples annealed at 230°C and 500°C are 8.5×10^-15cm².s^-1 and 3.0×10^-14cm².s^-1, respectively. The formation of the copper-silicide phase is observed by XRD, and its intensity becomes stronger with the increase of annealing temperature. For the Cu/SiO₂/Si (111) samples prepared by neutral clusters, the interdiffusion of Cu and Si atoms occurs and copper silicides are
formed when annealed at 450°C. The diffusion coefficients of Cu in Si are calculated to be 6.0×10^-16cm².s^-1 at 450°C, due to the fact that the existence of the SiO₂ layer suppresses the interdiffusion of Cu and Si.