Microstructure, electrical resistivity and stresses in sputter deposited W and Mo films and the influence of the interface on bilayer properties

Sputter deposited W, Mo and bilayers of W/Mo on Si were prepared by varying the deposition conditions in order to obtain 100 nm thick films with low electrical resistivity. Investigations showed that the depositions carried out at low pressures and at 400 °C substrate temperature led to the formation of films with lower resistivity and improved out-of-plane (110) preferred orientation of the grains. Bilayer films of W/Mo were deposited to study the template effect on the film resistivity. It was observed that sputter deposition of the heavier metal, W, on the lighter metal, Mo, resulted in both a higher interface intermixing and roughness as compared to the deposition of Mo on W. This effect is an outcome of the impact from the higher energetic Ar neutrals backscattered from a heavier target as compared to a lighter target. The energy of the backscattered gas neutral from W target is almost thrice that of other species which leads to a higher damage of the growing film. Resistivity values obtained for the bilayer films show that the order of deposition is crucial, in obtaining films with better interfacial properties especially in the case when the two materials have very different atomic weights, due to the formation of asymmetric interfaces.