Microstructure and Mechanical Properties of TaN Thin Films Prepared by Reactive Magnetron Sputtering

Reactive magnetron sputtering was used to deposit tantalum nitride (Ta-N) thin films on Si substrate. The effect of varying the N-2 percentage in the N-2/Ar gas mixture on the Ta-N film characteristics was investigated. Mechanical and tribological properties were studied using nanoindentation and pin-on-disc wear testing. Decreasing the N-2 content in the gas mixture was found to change the film structure from face centered cubic (fcc) TaN (from 25% to 10% N-2) to highly textured fcc TaN (at 7% N-2) to a mixture of fcc TaN1.13 and hexagonal Ta2N (at 5% N-2), and finally to hexagonal Ta2N (at 3% N2). A high hardness of about 33 GPa was shown by the films containing the hexagonal Ta2N phase (5% and 3% N-2). Decreasing the N-2 content below 7% N-2 was also found to result in microstructural refinement with grain size 5-15 nm. Besides the highest hardness, the film deposited with 3% N-2 content exhibited the highest hardness/modulus ratio (0.13), and elastic recovery (68%), and very low wear rate (3.1 x 10(-6) mm(3).N-1.m(-1)).