Reaction kinetics of nickel/silicon multilayer films

We report on the use of differential scanning calorimetry to study the temperatures and kinetics of nickel silicide formation from nickel/amorphous silicon multilayer films. When the layer thickness ratio of a multilayer film is 1:1, Ni2 Si is the only phase to form. The activation energy for this reaction is 1.5 eV and the interdiffusivity pre-exponential is found to be 6 cm-2s-1. These values are in excellent agreement with values obtained using different techniques. The temperature at which Ni 2 Si formation is observed a function of layer thickness, with the thinner layers reacting at lower temperatures. This layer thickness dependence can be explained by the lower reaction times for thinner layers. Upon mechanical impact, films composed of very thin layers (<125 Å) reacted explosively at room temperature to form Ni2 Si. Explosive silicidation is presumed to occur when the rate of heat generation at the many reacting interfaces exceeds the rate of heat dissipation.