Co silicide formation on epitaxial Si1-yCy/Si (001) layers

We investigated the formation and structure of cobalt silicide (CoSi2) on S i1-yCy (0 less than or equal to y less than or equal to 0.81%) layers grown by molecular beam epitaxy on Si (001). The incorporation of C in the Si la ttice causes the following phenomena during silicidation: (i) the formation of CoSi2 is delayed in temperature scale, as compared to pure Si; (ii) epi taxial CoSi2 grains are formed at T greater than or equal to 600 degrees C; (iii) a two sublayer structure of CoSi2 is observed, where the upper subla yer contains a very small amount of C and has a homogeneous microstructure, while the lower sublayer, which has a higher C concentration, contains ran domly oriented CoSi2 nanocrystallites; (iv) spatial inhomogeneity results i n significant variation (within +/- 40%) in the CoSi2 layer thickness; (v) no strain relaxation in the Si1-yCy layer during silicidation is detected u p to 700 degrees C; and (vi) the distribution of carbon and boron in the se miconductor during silicidation is not changed significantly. The two latte r findings show the potential of CoSi2 on Si1-yCy for device application de spite the mentioned inhomogeneity in CoSi2 microstructure. (C) 2000 America n Institute of Physics. [S0021-8979(00)00507-7].