Interfacial reactions of the Co/Si1-xGex system

Abstract

Thermal reactions of Co(200 Angstrom)/Si0.76Ge0.24(1500 Angstrom)/Si and Co(200 Angstrom)/Si0.54Ge0.46(1000 Angstrom)/Si systems in a vacuum of 1-2 X 10(-6) Ton. were studied. At temperatures above 200 degrees C Ge segregation appeared even though no silicides and/or germanosilicides were formed. At a temperature of 225-550 degrees C Co(Si1-yGey) was formed, in which the Ge concentration was deficient, The formation temperatures of CoSi2 in the Co/Si1-xGex systems, where x = 0.24 and 0.46, were above 575 degrees C, being relatively higher than that in the Co/Si system. At temperatures above 500 degrees C the island structure, Ge segregation to the surface of the exposed Si1-xGex films, and the penetration of reacted layer into the Si substrate occurred, At temperatures above 700 degrees C a SiC layer was grown on the film surface. For the Si0.54Ge0.46 films the penetration of the reacted layer into the Si substrate occurred even at 350 degrees C owing to the wave structure of the as-grown Si0.54Ge0.46 films. A Si layer interposed between Co and Si0.76Ge0.24 films is an effective scheme to grow a continuous CoSi, contact at 550-600 degrees C without inducing Ge segregation and hence the strain relaxation in the Si0.76Ge0.24 films.