Effect of Pd on the Ni2Si stress relaxation during the Ni-silicide formation at low temperature

The thermally induced solid-state reaction between a 50-nm-thick Ni(6%Pd) layer and a Si(100) substrate was investigated using in situ and simultaneous x-ray diffraction and sheet resistance. The reaction begins with the growth of the stressed δ-Ni2Si phase, and the transient θ-Ni2Si. At the end of the θ-Ni2Si consumption, a NiSi seed is formed. Then, the δ-Ni2Si relaxation occurs simultaneously with its subsequent growth and the Pd out diffusion from the unreacted Ni(Pd) layer. It is suggested that the driving force for the Pd diffusion out of the metal layer is linked to both the higher solubility of Pd in NiSi compared to Ni2Si and to the Ni2Si relaxation.