A high-resolution transmission electron microscopy study on the structure of cobalt disilicide/Si(111) interface has been carried out.
The boron-doped p-type Si(111) substrates were cleaned prior to crystal growth by current-pass-heating in order to obtain an atomically clean surface. Co (99.9 %) films were deposited on Si(111) substrates in an ultrahigh vacuum chamber with a base pressure of ∼1×$10^{-10}$ Torr at room temperature. And then the wafers were in situ annealed.
When the deposited films were annealed at 500 ∼ 550℃, the interface between $CoSi_2$ and Si was found to have lump-shaped. In the sample annealed at 600℃, the lump-shaped interface was decreased in both size and number. The lower part of the lump-shaped interface was flattened and was parallel to (111) plane. The lump-shaped interface was not observed and several kinds of facets were formed in the sample annealed at 700℃. The facet parallel to Si($11\overline{1}$)//B-$CoSi_2$($\overline{1}\overline{1}5$) plane were observed in several samples. In addition, two new facets, Si(001)//B-$CoSi_2$($22\overline{1}$) and Si(114)//B-$CoSi_2$(110) that have not been reported were found. Dramatic decrease in the roughness of the interfaces and atomically flat interface with steps were observed in the sample annealed at 750℃. Most of steps had a height of only 2∼3 {111} atomic planes. As a result, they had more flat interface when the $CoSi_2$ films were annealed at higher temperature.
