Formation and evolution of nickel silicide in silicon nanowires

Thermally activated axial intrusion of nickel silicides in silicon nanowires (SiNWs) is utilized to form nickel silicide/silicon contacts in SiNW field effect transistors. The growth of different nickel silicides is often accompanied by local thickening and tapering of the NW, up to its full disintegration. In this paper, this process was investigated in SiNWs of 30-60 nm in diameters with prepatterned Ni electrodes after annealing cycles at different temperatures of 300 °C-440 °C and times up to 120 s. From the temperature dependence of the intrusion lengths, activation energy of 1.45 eV for the surface diffusion of nickel was extracted. In several cases, periodic thickening of the nickel-rich part is accompanied by tapering of the monosilicide part up to its full dissolution. The kinetics of the nickel silicides growth was described by phenomenological model. For a certain set of parameters, tapering and dissolution of the monosilicide part of the intrusion were predicted, similar to the experimental results.