Cobalt titanium nitride amorphous metal alloys by atomic layer deposition

Highlights: • Cobalt titanium nitride (CoTiN) deposited by ALD shows amorphous metallic phase. • Unidirectional interlayer formation is observed from Co to TiN at the interface. • ALD CoTiN shows enhanced thermal stability compared with that of ALD Co. • Improved mechanical hardness of ALD CoTiN is observed compared with that of ALD Co. The formation of thin amorphous cobalt titanium nitride (CoTiN) layers was investigated using a supercycle method of atomic layer deposition (ALD). The stoichiometry of the resultant ALD CoTiN films was controlled by changing the ratio of Co and TiN thicknesses. X-ray diffraction analysis and transmission electron microscopy observations showed that the microstructure of the ALD Co and TiN was transformed from polycrystalline to amorphous CoTiN. The stoichiometry of the CoTiN layer was affected by the growth characteristics of ALD Co and TiN on each surface. The results revealed that ALD TiN undergoes nucleation incubation on the ALD Co surface, whereas ALD Co does not undergo nucleation incubation on the ALD TiN surface. The properties of the amorphous CoTiN layers were evaluated by diffusion experiments and mechanical tests. Because of the lack of grain boundaries, the CoTiN efficiently blocks the diffusion of Cu at elevated temperatures and exhibits higher hardness compared with ALD Co.