PHASE-FORMATION BETWEEN CODEPOSITED CO-TA THIN-FILM AND SINGLE-CRYSTAL SILICON SUBSTRATES

150 nm films of Co and Ta were electron gun codeposited onto Si (100) and Si (111) substrates. The reactions of the components of the amorph ous film were studied in the temperature range 873-1373 K by X-ray dif fraction and transmission electron microscopy. The first phase to crys tallize from the amorphous film was Co2Ta which is stable in the tempe rature range 873-1073 K. CoSi appeared at 973 K and was stable up to 1 073 K. The end products of the heat treatment were CoSi2 close to the Si substrate and TaSi2 as the outer layer. Complete separation of the silicides occurred, as expected from a system comprising a refractory metal and a near-noble metal on Si substrate. Reactions on Si (111) oc cur at a faster rate than on Si (100). These take place at higher temp eratures than the formation temperatures of the respective silicides i n the binary systems. No CoTaSi ternary phase was observed in the pres ent work.