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 N2 percentage in the N2/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 N2 content in the gas mixture was found to change the film structure from face centered cubic (fcc) TaN (from 25% to 10% N2) to highly textured fcc TaN (at 7% N2) to a mixture of fcc TaN1.13 and hexagonal Ta2N (at 5% N2), 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% N2). Decreasing the N2 content below 7% N2 was also found to result in microstructural refinement with grain size 5–15 nm. Besides the highest hardness, the film deposited with 3% N2 content exhibited the highest hardness/modulus ratio (0.13), and elastic recovery (68%), and very low wear rate (3.1 × 10−6 mm3·N−1·m−1).