Formation of cobalt silicide spikes in 0.18 μm complementary metal oxide semiconductor process

Co silicide spikes have been found in active contact salicidation in complementary metal oxide semiconductor devices during failure analysis by means of transmission electron microscopy examination. Scanning transmission electron microscopy, energy dispersive x-ray analysis and microdiffraction study revealed that these spikes are CoSi2with an epitaxial relationship with Si of (111)CoSi2//(111)Si and [11̄0]CoSi2//[11̄0]Si. The formation of the CoSi2spikes are suspected to be due to the presence of undesired SiOx residue between Co film and Si substrate which acts as a solid diffusion membrane to cause the Si rich phase CoSi2to precipitate directly inside Si lattice.