Mechanical and Structural Behavior of HfN Thin Films Deposited by Direct Current and Mid-Frequency Magnetron Sputtering.

Nanocrystalline HfN thin films were deposited onto silicon substrates with direct current magnetron sputtering (dcMS) and mid-frequency magnetron sputtering (mfMS) by using hafnium metallic target with 3-inch diameter and 99.9% purity in argon/nitrogen atmosphere, under 4 different pulse frequencies and duty cycles. In order to evaluate the structural, morphological and mechanical properties, we used X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), nanoindentation tests. X-ray diffraction patterns show that films sputtered in dcMS mode have a mixed -HfN and HfN phases, whereas mfMS favor a single -HfN phase. mfMS leads to films with the higher mechanical hardness and smaller surface roughness than those of films deposited by dcMS. Hafnium nitride films with a single -HfN phase show the highest hardness values of 24.5 GPa while those of mixed -HfN and HfN phases show the lowest 18.3 GPa. In summary, the sputtering technique has a crucial role on the properties of the film and can be suitable used to adjust the structure and hardness of HfN films.