OMCVD OF COBALT AND COBALT SILICIDE

Cobalt and cobalt silicide layers were deposited by OMCVD using the Co precursors Co(C5H5)2, Co2(CO)8, Co(C5H5)(CO)2 and CoCF3(CO)4, and the Si precursors SiH4 and Si2H6. Strongly textured (111)-beta Co layers were grown from Co(C5H5)2, Co(C5H5)(CO)2 and CoCF3(CO)4 at temperatures above 300-degrees-C in H2 at atmospheric pressure. Growth from Co(C5H5)2 is inhibited on Si substrates. For temperatures greater-than-or-equal-to 600-degrees-C to Co layers deposited from Co(C5H5)(CO)2 react with the Si(100) substrate to form CoSi2(00l) aligned with the substrate orientation. Co2(CO)8 gives amorphous Co between 200 and 300-degrees-C. The upper temperature is set by the occurrence of homogeneous gas-phase reactions at atmospheric reactor pressure. Cobalt silicide layers can be grown from Co2(CO)8 and (di)silane at temperatures between 200 and 400-degrees-C. The Co/Si ratio in the layers decreases with increasing temperature and is independent of the gas-phase Co/Si ratio. Stoichiometric CoSi2 is obtained at approximately 300-degrees-C. Both Co(C5H5)2 and Co(C5H5)(CO)2 react with (di)silane, leading to the incorporation of carbon in the layer. The Co/Si ratio and the carbon content in the layers are practically independent of the deposition conditions. With CoCF3(CO)4 no contamination-free silicide could be grown. The carbon incorporation with Co(C5H5)2 and Co(C5H5)(CO)2 can be avoided by a pulsed growth method in which the Co precursor and the Si precursor are introduced alternately into the reactor. With Co(C5H5)2 the growth is then inhibited on Si substrates.