Studies on magnetron sputtered niobium thin films: influence of deposition angle of sputtered atoms

The present study investigated the influence of deposition angle of sputtered atoms on the microstructure, morphology, mechanical and electrical properties of niobium (Nb) thin films by varying it from 0 degrees to 50 degrees in a step of 10 degrees. It was found that the deposition rate follows cosine distribution with deposition angle. The root mean square (rms) surface roughness increases from 0.40 +/- 0.05 to 1.5 +/- 0.2 nm, and density decreases from 8.5 to 7.7 (+/- 0.2) g/c.c as the deposition angle increases while no significant change in crystallites size was observed. Room temperature electrical resistivity rises from 79 to 293 mu ohm-cm with increasing deposition angle due to enhanced electron scattering. The residual stresses remain compressive but shift towards tensile as the deposition angle increases. Atomic force microscopy confirms the increase in surface roughness and showing columnar growth at higher deposition angle. This work provides some insights into the how the deposition angle of sputtered atoms affects the growth of Nb films and optimal deposition angular range of sputtered atoms to coat Nb films on irregular surfaces.