Effects of surface defects on the orientation of NiSi2 formed on Si (111) substrates

Abstract

The effects of surface reconstruction, surface steps, and deposition temperature on the growth of NiSi2 on Si(111) have been investigated using low-energy electron diffraction and Auger electron spectroscopy. Surface reconstruction was changed by diffusion of Ni into the substrate, forming a ((19)1/2×(19)1/2) R±23.4° structure. On planar (unstepped) Si(111), the formation of the two domains of NiSi2 occurs under the same conditions on the (19)1/2 and the clean surface (7×7) reconstructions. On vicinal (stepped) Si(111), different step structures form on the clean and Ni-diffused surfaces. The growth of NiSi2 proceeds differently on the two step structures, both cases being different from growth on the planar surfaces. Specific types of step edges, 〈11̄0〉 vs 〈1̄1̄2〉, appear to favor formation of type B or type A silicides, respectively. At deposition temperatures above 200 °C, a considerable amount of Ni diffuses into the Si substrate without reacting. However, the orientation of the silicide which does form is the same as at lower deposition temperature.