Copper tantalum nitride (CuTaN₂) thin films prepared by reactive radio-frequency magnetron sputtering

RF reactive sputtering was used to deposit copper tantalum nitride (CuTaN₂) films from a Cu/Ta target in an environment containing a mixture of argon and nitrogen at two different substrate temperatures: room temperature and 200 °C. The films were studied by SEM, EDS, XRD, Raman spectroscopy, spectrophotometry, and resistivity measurements. The deposition conditions significantly impacted the morphology of the films, which varied from smooth, void-free films at high nitrogen concentrations and at room temperature substrates to cauliflower-like grains with voids at low nitrogen contents and elevated substrate temperatures. Despite the target’s 1:1 Cu: Ta ratio, the stoichiometric analysis showed a lower Ta content in the deposited film. The films produced on silicon substrates were polycrystalline, whereas those deposited on glass substrates were amorphous. The band gap (0.9 eV to 1.55 eV) and film resistivity (20 kΩ-cm to 76 kΩ-cm) are strongly affected by the nitrogen fraction in the sputtering gas. Increasing the nitrogen percentage in semiconductor films results in smoother films with larger bandgaps (approximately 1.5 eV), higher resistivity, and compositions closest to those of stoichiometric CuTaN₂.