Surface morphology and electric conductivity of epitaxial Cu(100) films grown on H-terminated Si(100)

We have investigated the crystal structure, surface morphology, and electrical conductance of Cu films grown on H-terminated Si(100). The films were grown by thermal evaporation at 10(-8) Torr, at deposition rates from 0.1 to 3.5 nm/s and at substrate temperatures from room temperature up to 200 degrees C. Typical film thicknesses were similar to 100 nm. Epitaxial growth was verified by x-ray diffraction for films grown near room temperature at rates up to 2 nm/s. The root-mean-square surface roughness was measured to be 1-2 nm using atomic force microscopy (AFM). Higher growth rates or deposition temperatures above 100 degrees C produced poor quality, nonepitaxial films. Postdeposition annealing at temperatures up to 175 degrees C did not improve the surface roughness, and at higher annealing temperatures rapid silicide formation destroyed the Cu film. In situ electrical resistance measurements and AFM images suggest that for about the first 6 nm of-growth the film consists of disconnected islands. X-ray-diffraction data show that the islands consist of crystalline Cu; there is no evidence for a silicide layer. At higher thicknesses the film consists of Cu with an impurity concentration of a few tenths atomic percent. The thickness dependence of the electrical conductance implies a high level of surface, interface, or grain-boundary scattering, characterized by a near-zero apparent specularity parameter p. (C) 1996 American Institute of Physics.