Competing Initial Reactions at Transition-Metal/Silicon Interfaces

Abstract

The process of suicide formation by contact reaction at metal/Si interfaces normally involves rather uniform motion of the growth fronts which separate metal, suicide, and Si regions, as has been observed for suicide growth in many transition-metal/Si systems. At lower temperatures, however, the reaction behavior can be complicated significantly by the presence of other material reactions which may compete with interfacial suicide formation. For refractory metals, strong interfacial mixing over considerable depth (~ 100 Å or more) is observed at temperatures too low for the normal interfacial suicide formation process to contribute; the highly nonuniform character of this reaction, as shown by ion scattering and TEM studies, suggests that other material reactions (e.g., grain boundary diffusion) must dominate the interfacial chemistry at low temperature. In a similar way, anomalous and nonuniform reaction behavior during the low temperature deposition of initial transition metal layers on Si apparently involves surface diffusion processes which are faster than interfacial suicide formation.