Effects of Nitrogen Content on the Phase and Resistivity of TaN Thin Films Deposited by Electron Beam Evaporation
A series of amorphous electron beam evaporated Ta and TaN films with N/Ta ratio from 0 to 1.15 were deposited on Si/SiO2 substrates at 200°C. As N/Ta ratio increases, the TaN films undergo phase changes from pure metallic Ta to a mixture of Ta, Ta2N, and nitrogen-rich TaN films. The electrical resistivity of the Ta and TaN films increased from 242 µΩ-cm to 1126 µΩ-cm with increasing N/Ta ratio. X-ray diffraction patterns revealed the development of different phases of TaN that are in agreement with the TaN phase diagram. The presence of different phases on the film surface was also confirmed by x-ray photo-emission spectroscopy (XPS) analysis. Groups of Ta4f doublet related to different TaN phases were observed in the core-level spectra of TaN films. Field-emission scanning electron microscopy images revealed that surface morphology also varied with the phase change in TaN films. The N/Ta ratios from energy-dispersive x-ray generally agreed with those from the XPS analysis.