Study on dc magnetron sputter deposition of titanium aluminium nitride thin films: Effect of aluminium content on coating

Titanium aluminium nitride thin films have been deposited on glass slides using a dual unbalanced d.c. magnetron sputter arrangement with separate titanium and aluminium targets. A range of Ti/Al/N compositions were produced by varying the aluminium target magnetron current. The thin films were then examined using an atomic force microscope (AFM) and a held emission scanning electron microscope. Aluminium, titanium and nitrogen compositions (wt.%) were determined by using energy dispersive X-ray spectroscopy. It was found that as the aluminium magnetron current increased from 0.1 to 0.4 A, the titanium decreased from 77 wt.% to 53 wt.%, the aluminium increased from 6 wt.% to 25 wt.% and the colour changed from gold to a blue-grey. An increase in the aluminium content had a significant effect on the grain size of the film. Surface measurement analysis using the AFM results revealed that as the aluminium content increased both the rms roughness (6.5 nm-->3.2 nm) and grain size (120 nm-->90 nm) decreased. It is believed that the above effects could result from the increase in aluminium atom bombardment rate with the higher aluminium magnetron current.