Growth of epitaxial CoSi2 on SiGe(001)

A technique for achieving epitaxial growth of (001)-oriented CoSi2 on strained epitaxial layers of Si1-xGex(001) is described. The technique is based on a variation of the template method, and is designed to control the local environment of Co atoms at the CoSi2/SiGe interface. The effects of the Co-Ge interactions on the interfacial reaction and the epitaxial orientation and the morphology of the silicide film were investigated. This reaction was found to cause pitting in (001)-oriented CoSi2 films, and to stabilize the (22(1) over bar) orientation for films codeposited under conditions where CoSi2(001) growth is achieved on Si(001) substrates. The (22(1) over bar)-oriented CoSi2 films were islanded after annealing at 700 degrees C. The islands were terminated by ((1) over bar 11) and (110) facets inclined at 15.8 degrees and 19.5 degrees, respectively, from CoSi2 [22(1) over bar] towards CoSi2 [114]. These results were interpreted in terms of reduction of interfacial and surface energies, and geometric effects. Silicide films up to 730-Angstrom-thick were deposited and annealed up to 900 degrees C. The films were stable against agglomeration, and retained tensile stress in the CoSi2 layer after annealing at 700 degrees C. The rms roughness of the CoSi2 films was comparable to that of the Si(001) substrate-less than 15 Angstrom over areas as large as 20X20 mu m(2). Films annealed at 900 degrees C were severely agglomerated. (C) 1999 American Institute of Physics. [S0021-8979(99)06714-6].