Kinetics of Ni3Si2 formation in the Ni2Si–NiSi thin film reaction from in situ measurements.

The kinetics of Ni₃Si₂ formation in the Ni₂Si–NiSi thin film reaction were determined from simultaneous in situ x-ray diffraction (XRD) measurements, performed using a synchrotron source, and sheet resistance measurements. Samples consisted of 90 nm Ni/100 nm polycrystalline-Si/SiO₂ stacks, of interest for fully silicided gate applications, on (100) Si. After initial formation of a Ni₂Si/NiSi bilayer, these films reacted to form Ni₃Si₂. The evolution of sheet resistance and of the intensity of XRD peaks were used to extract the fraction of Ni₃Si₂ formed during ramp and isothermal annealings. A Kissinger analysis was performed for ramp annealing with ramp rates of 1, 3, 5, 9, and 27 °C/s, obtaining the activation energy of Ni₃Si₂ formation, E_a=1.92±0.15 eV. A Kolmogorov-Johnson-Mehl-Avrami analysis was performed for isothermal anneals, finding an Avrami exponent of 2.1±0.2, suggesting two-dimensional growth. This is consistent with a nucleation controlled process for Ni₃Si₂ formation, with nucleation sites at different positions in the thin film, and subsequent lateral two-dimensional propagation of the transformation front parallel to the film surface. Implications for Ni fully silicided gate applications are discussed. [ABSTRACT FROM AUTHOR]