Influence of substrate temperature and N₂/Ar flow ratio on the stoichiometry, structure and hardness of TaNx coatings deposited by DC reactive sputtering

Abstract

The effect of substrate temperature and N2/Ar flow ratio on the stoichiometry, structure and hardness of TaNx coatings prepared on (111) Si substrates by DC reactive sputtering was investigated. For the structural, chemical and morphological analysis, X‐ray diffraction (XRD), Auger electron scanning and atomic force microscopy were respectively used. Hardness values of thin films were determined using the work of indentation model from nanoindentation measurements. TaN stoichiometric coatings were obtained for samples deposited at room temperature. The stoichiometric TaN phase was not obtained by increasing the temperature up to 773 K, even when increasing the N2/Ar flow ratio. Even when a saturation in nitrogen content was achieved, nitrogen vacancies are still present in those samples. For coatings prepared at 773 K and low N2/Ar flow ratio, a phase mixture between TaNx and cubic α‐Ta was observed, while a cubic structure δ‐TaN was formed by increasing the N2/Ar flow ratio. A maximum in hardness and (38 GPa) was obtained for the sample deposited at 773 K and a N2/Ar flow ratio of 0.2, which presented a δ‐TaN cubic crystalline structure and a roughness value of 1.6 nm. Copyright © 2015 John Wiley & Sons, Ltd.

Nonstoichiometric Multicomponent Nitride Thin Films

“…Generally, the hardness of quinary and higher-order nitrides of the same groups (Group 4 and 5) is considerably higher than the hardness of the binary constituents [46] . For near-stoichiometric nitrides, in Figure1.2, the Group 4 binary nitrides generally have higher hardness than those of Group 5, which is related to the greater contribution of M-N bonding in group 4, but in substoichiometric range, TaN0.4 [47] and NbNx [48] (0.92 > x > 0.75) with stronger interstitial effects have higher hardness than TiNx and ZrNx, due to different interstitial effects. This suggests that there are more possibilities to increase hardness in substoichiometric ends, which may generate a stoichiometry-hardness trade-off in future multicomponent nitride films.…”

Effect of Bias Voltage on Microstructure and Properties of Tantalum Nitride Coatings Deposited by RF Magnetron Sputtering

“…However, TaN x coating synthesized by reactive magnetron sputtering shows a variety of the stoichiometry, such as Ta 2 N, TaN, Ta 4 N 5 , and Ta 5 N 6 , due to its defective structure, i.e., high vacancy concentrations of atomic lattice sites can be present during the synthesis of TaN x thin coatings [5][6][7][8]. It is believed that the chemical composition and crystalline structure of the as-deposited TaN x coatings strongly depend on the deposition technique and the process parameters, such as sputtering power source (e.g., DC [4], RF [9], pulsed power [10]), N 2 /Ar ratio [11], bias voltage [12], substrate temperature [13], pressure [14] in the growth chamber, etc.…”

Thermal treatment of (TiZr)N coatings on CO2‐controlled atmosphere

“…The literature has evidenced that nitrogen deficiency increases hardness values. For example, in the TaN x coatings, when the stoichiometry measurement was x = 0.53, a hardness of 38 GPa is obtained, which is higher than TaN coatings 46 . Besides, if the TiN x , TiO x , and TiON x compounds found here are treated, as compounds substoichiometric, we could say that these are super‐hard materials due to blocking the slip grain border 47 .…”