Studies on phase dependent mechanical properties of dc magnetron sputtered TaN thin films: evaluation of super hardness in orthorhombic Ta₄N phase

Abstract

The mechanical hardness of the different phases of tantalum nitride (TaNx, x ≤ 1) thin films grown by the reactive planar dc magnetron sputtering technique at 300 °C have been evaluated. The different phases have been prepared by varying the nitrogen (N2) to argon (Ar) gas ratio R in the range 0.04–0.30. The phases present in each sample and their volume fractions are obtained from x-ray diffraction and Ta 4f7/2 binding energy x-ray photoelectron spectra, respectively. The grown TaN thin films are found to contain mainly cubic-TaN0.1, orthorhombic-Ta4N, orthorhombic-Ta6N2.5, hexagonal-TaN0.8 and cubic-TaN phases. The hardness corresponding to each phase has been derived from the experimental hardness values using ‘rule of mixtures’. A super hardness of ∼61.9 GPa is observed in orthorhombic Ta4N phase. With increase in R, a decrease in the surface oxidation of TaN has been observed. The reduced surface oxidation is attributed to the formation of stoichiometric TaN thin films. The surface morphology is found to change considerably with increase in R.

Study on microstructural, chemical and electrical properties of tantalum nitride thin films deposited by reactive direct current magnetron sputtering

“…This finding indicates that the increase of the nitrogen content in sputter gas seems to have a similar effect like a conventional cooling of the substrate. In accordance to our investigations, the evolution of TaN x film morphology with N 2 flow is reported in a different study (Valleti et al 2008). …”

“…The problem indexing sputtered TaN x phases is well known, as in the JCPDS Database more than 30 reference patterns for TaN x films are listed which differ only slightly in the occurrence and the position of peaks. The indexing is even more complicated, as a pure tantalum nitride in the crystallographic sense is not generated with sputter deposition technique, so that there is always a mixture of different phases present in the films (Valleti et al 2008). By solely knowing the diffractogramm of TaN_20 the presence of many different crystallographic planes is possible, as listed in Table 6.…”

“…Basically, for a low nitrogen concentration in the deposition chamber, phases such as Ta 2 N (Lu et al 2001b;Shin et al 2002;Valleti et al 2008;Chang et al 2002), TaN 0.1 (Shin et al 2002;Valleti et al 2008) and TaN (Chang et al 2002), are reported, but also the presence of N-saturated a-Ta can be found which changes to Ta 2 N (Chang et al 2002). In our case the presence of a pure tantalum phase within the TaN_20 samples can be excluded when compared to results gained under similar deposition conditions (Grosser and Schmid 2009).…”

Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate

“…Magnetron discharges are widely used for thin film deposition in surface treatment 1,2 , magnetic and superconducting devices 3 , semiconductor industry 4 and in surface coating engineering of materials under low temperature conditions 5,6 . In these systems, the magnetic field, usually produced by placing permanent magnets behind the cathode, confines the plasma in the near cathode region, reducing the electron loss to the sidewalls.…”

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

“…The reported values of hardness for various phases of Ta-N thin films, such as hex Ta 2 N, fcc TaN, orth Ta 6 N 2.5 and orth Ta 4 N are 31, 20, 30.8, and 61.8 GPa, respectively [19][20][21][22][23][24][25].…”