Interfacial reactions of the Co/S& -xGex system

Thermal reactions of Co(200 A) /Si0,76Ge0,24( 1500 A) /Si and Co(200 A) /Si0,54Ge0,46( 1000 A) /Si systems in a vacuum of l2 X 10m6 Torr were studied. At temperatures above 200°C Ge segregation appeared even though no silicides and/or germanosilicides were formed. At a temperature of 225-550°C Co(Si, -vGe,) was formed, in which the Ge concentration was deficient. The formation temperatures of CoSi, in the Co/Si,-,YGe, systems, where x=.0.24 and 0.46, were above 575”C, being relatively higher than that in the Co/Si system. At temperatures above 500°C the island structure, Ge segregation to the surface of the exposed Sil -,rGe,Y films, and the penetration of reacted layer into the Si substrate occurred. At temperatures above 700°C a Sic layer was grown on the film surface. For the Si054Ge0,46 films the penetration of the reacted layer into the Si substrate occurred even at 350°C owing to the wave structure of the as-grown Si0,54Ge0,46 films. A Si layer interposed between Co and Si 0,76Ge0.24 films is an effective scheme to grow a continuous CoSi, contact at 550-600°C without inducing Ge segregation and hence the strain relaxation in the Si0,76Ge0,24 films.