The growth of an intermediate CoSi phase during the formation of epitaxialCoSi2 by solid phase reaction

Among the epitaxial transition metal silicides CoSi2 is of special interest for applications in ULSI technology due to its high thermal stability and low electrical resistivity. The solid phase reaction of metallic bilayers w ith Si in an N-2 ambient is a well-known process for growing epitaxial CoSi 2. However, the real function of the so-called diffusion barrier, which is arising during the annealing process, remains unclear. TEM studies revealed the intermediate, growth of a CoSi phase with grains of preferred orientat ion to Si. The growth of this phase raises the temperature of CoSi2 nucleat ion, which starts at the CoSi/Si interface. The nucleation temperature dete rmines the quality of the growing epitaxial CoSi2, which is better for Ti a s a barrier forming material than for Hf, also used successfully. Whether a n intermediate oriented growth of CoSi is promoting the epitaxial quality o f CoSi2 otherwise than by shifting the nucleation temperature, remains an o pen question. (C) 1998 Elsevier Science S.A. All rights reserved.