Reaction of Mo Thin Films on Si (100) Surfaces

The reaction between Mo thin films and single crystal Si (100) substrates has been studied as a function of various heat‐treatments. In the temperature range between 520° and 550°C, MoSi 2 has been observed to grow linearly with time and with an activation energy of about 4.1 eV. X‐ray diffraction indicates that the hexagonal phase of MoSi 2 changes continuously to the tetragonal phase as the temperature increases from 600° to 800°C. In contrast, the presence of native oxide prohibits formation of any silicide phases in the above temperature range and leads to the formation of a Mo 3 Si phase at temperatures near 1000°C. The formation of MoSi 2 results in large compressive strains in the MoSi 2 layer and in strains of the opposite sign in the underlying Si. In limited reaction areas the corresponding stresses were found to be sufficient to cause the nucleation and propagation of dislocations in the Si substrates. The dislocations are propagated for considerable distances away from the reaction areas. An anomalous growth of silicide occurs at the edges of the reaction areas. These phenomena are shown to result from cumulative stress effects. Stresses enhance the formation of MoSi 2 layers, and thereby modify the kinetic laws of growth.