Abstract
The relatively small lattice mismatch (~ 1.2 %) between CoSi2 and Si and the similarity in crystal structure allow the possibility of growing epitaxial CoSi2 layer on Si. Therefore CoSi2 has a great advantage to be used in semiconductor technology. There are several reported methods in controlling the formation process of epitaxial CoSi2 on Si. And each method has various experimental factors to form different CoSi2 structures. In order to make a systematic understanding on the effect of each experimental factor on the growth of cobalt silicides, nominal thicknesses of cobalt, deposition rates and growth temperatures were changed separately in this thesis. The effect of nominal thickness of Co layers on the growth of the epitaxial CoSi2 islands using reactive deposition epitaxy was investigated. It was found that the nucleation density of CoSi2 and the average size of CoSi2 islands increase with increasing the nominal thickness of the Co layers from 0.3 nm to 0.5 nm. As the average size of CoSi2 islands increases, the distribution range of width and length of the CoSi2 islands become larger as well. In addition, CoSi2 islands containing both the A-type interfaces and the B-type interfaces coexisted and nucleated independently during growth. The number of B-type (twinned) interfaces is much greater than that of the A-type (untwinned) interfaces. It was found that, as the deposition rate increases (0.003 nm/sec – 0.005 nm/sec), the average length of CoSi2 islands is shorter but the distribution range of the width is the same. So the distribution range of width is independent on the deposition rate. Besides, the nucleation density of CoSi2 islands increases dramatically with increasing the deposition rate until it is close to the saturation. Moreover, the percentage of the B-type interfaces is higher with increasing deposition rate as well. It was found that, as the substrate temperature increased from 750 ℃ to 820 ℃, the average size and the aspect ratio of CoSi2 islands were larger and the nucleation density decreased.