Study of CoSi2 Formation from a Co-Ni Alloy

CoSi formation from Co–Ni alloys with 25 and 10% Ni content was investigated. Samples with various 2
Co–Ni /Ti stacks were characterized by four-point probe, AES, XRD, RBS and TEM. Light scattering
measurements were carried out for roughness evaluation. Stress build-up was estimated from room temperature
measurements of wafer curvature. It was found that Co disilicide formation temperature decreases with an
increase of the Ni percentage. CoSi growth at temperatures around 450–5008C depending on Ni concentration 2
and Ti cap thickness was observed. Sheet resistance of 5–6.5 V/ sq. was measured for various Co–Ni / Ti
compositions. CoSi (220) and CoSi (111) peaks were detected on XRD spectra for both Ni-rich and Ni-poor 2 2
layer. Stress values of 0.9–1.9 GPa were calculated for silicidation of various Co–Ni /Ti stacks. The roughness
of the silicide film was found to be dependent on Ni concentration, Ti cap thickness and anneal temperature.