Reactive sputtering deposition and characterization of Ta-N thin films

Tantalum nitride (Ta-N) films were deposited by reactive sputtering of tantalum in a nitrogen/argon gas mixture at three different gas ratios and two different substrate temperatures. SEM, EDS, XRD, and optical spectrophotometry measurements were used to assess this deposition technique as part of ongoing and future work on the fabrication and characterization of Ta-N-containing ternary alloy films and device structures. The results showed that increasing the substrate temperature and the N-fraction in the sputtering gas mixture led to finer grain morphology and denser film structure. The films were found to be amorphous with no substrate heating. For substrate temperature of 300 degrees C, the films were amorphous for N-fraction of 0.5 and crystalline for N-fraction of 0.17 or 0.83. The optical bandgap values obtained from spectrophotometry measurements showed a substantial variation with substrate temperature and nitrogen gas fraction from 1.62 to 2.1 eV.