Structure and property of magnetron sputtered ternary cobalt–nickel silicide films

Abstract

Ternary cobalt–nickel silicide films were prepared using magnetron sputtering from an equiatomic cobalt–nickel alloy target on Si substrate. The effect of post-deposition annealing on the phase formation, structural properties and resistivity of the resultant films has been studied. The results of XRD show that the annealing temperature and impurity level of oxygen play a crucial role in controlling the phase transformation of ternary silicide. Silicide phases are absent in the as-deposited film due to the amorphous nature. At relatively low annealing temperature, the phase of CoNi 3Si (2 2 0) and CoNiSi (2 2 0) coexist. With the increase of annealing temperature, the phase of CoNi 3Si (2 2 0) begins to transform into CoNiSi (2 2 0). At high annealing temperature (800 °C), only the phase of CoNiSi 2 (2 2 2) is formed. For Co–Ni silicide film annealed in pure argon gas ambient, two Raman peaks at 1357 cm −1 and 1591 cm −1 are attributed to the vibrational mode of CoSi 2 and NiSi 2 compounds. For ternary silicide annealed in atmosphere ambient, two Raman peaks located at 538 cm −1 and 690 cm −1 were observed and may be related to Si oxide or Co–Ni oxide. The 3D views of AFM images show that the surface roughness is relatively low when the silicidation temperature is smaller than 550 °C. After silicidation in 800 °C, the surface roughness increases abruptly. The resistance initially decreases with the increase of annealing temperature, and achieves minimum value (19 μΩ cm) in temperature ranges 500–550 °C. When the annealing temperature increases from 600 °C to 800 °C, the resistivity was found to increase slightly to 26 μΩ cm. The ternary silicide shows a temperature window for low resistivity as compared to binary NiSi.