Co-deposition of cobalt disilicide on silicon–germanium thin films

Abstract

The formation of CoSi 2 on strained epitaxial Si 0.8Ge 0.2/Si(100) films has been studied as a function of the deposition method and annealing temperature. Two types of deposition processes were used: a direct method, where 5 nm of pure Co metal were deposited at room temperature onto a strained 80 nm thick Si 0.8Ge 0.2 layer; and a co-deposition method, where 5 nm Co and 18.2 nm Si were simultaneously deposited in a 1:2 ratio onto a strained Si 0.8Ge 0.2 layer at 450°C. Samples were then annealed at temperatures ranging from 500 to 800°C. Extended X-ray absorbance fine structure spectroscopy (EXAFS) and X-ray diffraction (XRD) were used to characterize the structure of the resulting films. It was found that the samples prepared via the direct deposition method did not convert to CoSi 2 at any annealing temperature up to 800°C, while the co-deposited samples formed epitaxial CoSi 2 at even the lowest annealing temperature of 500°C. These results are discussed in terms of proposed reaction mechanisms of the different deposition methods, based on consideration of the Co–Si–Ge ternary phase diagram.