CODEPOSITION OF COBALT DISILICIDE ON SILICON-GERMANIUM THIN-FILMS

The formation of CoSi2 on strained epitaxial Si0.8Ge0.2/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 met hod, where 5 nm of pure Co metal were deposited at room temperature on to a strained 80 nm thick Si0.8Ge0.2 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 Si0.8Ge0.2 layer at 450 degrees C. Samples were then annealed at temperatures ranging from 500 to 800 degrees C. Exten ded X-ray absorbance fine structure spectroscopy (EXAFS) and X-ray dif fraction (XRD) were used to characterize the structure of the resultin g films. It was found that the samples prepared via the direct deposit ion method did not convert to CoSi2 at any annealing temperature up to 800 degrees C, while the co-deposited samples formed epitaxial CoSi2 at even the lowest annealing temperature of 500 degrees C. These resul ts are discussed in terms of proposed reaction mechanisms of the diffe rent deposition methods, based on consideration of the Co-Si-Ge ternar y phase diagram. (C) 1998 Elsevier Science S.A. All rights reserved.