Formation of (CoxNi1−x)Si2 ternary silicide by thermal annealing of evaporated Co/Ni thin films on Si substrate

• The reaction between Co/Ni and a Si substrate has been studied.
• Nickel starts reacting with Si to form Ni2Si and then converts to NiSi.
• Formation of (CoxNi1−x)Si2 by the diffusion of Co atoms in Ni silicides at 500 °C.
• The Co/Ni/Si system maintained its sheet resistance below 4.5 Ω/sq up to 800 °C.
• Shift in Raman peaks positions confirm the formation of (CoxNi1−x)Si2.

In this work, we studied the formation and the thermal stability of a ternary silicide (CoxNi1−x)Si2, obtained by thermal annealing. Ni and Co thin films were deposited on Si(100) substrate. The performed annealing of 30 nm-Co/15 nm-Ni/Si(100) samples is carried out by means of a conventional furnace during 20 min and a temperature range 300–800 °C. The obtained specimens were investigated using X-ray diffraction (XRD), Raman spectroscopy and Rutherford backscattering spectroscopy (RBS). XRD data showed that the formation temperature of the ternary (CoxNi1−x)Si2 phase was relatively lower compared with those of the NiSi2 and CoSi2 disilicides and it maintained its sheet resistance below 4.5 Ω/sq. Furthermore, the formation of this ternary silicide was confirmed by a shift in peaks position in the Raman spectra toward the lowest wavenumbers when the temperature is increased up to 500 °C. RBS results indicated that the thickness of the formed (CoxNi1−x)Si2 layer was approximately 28–52 nm.