Synthesis and high temperature XRD studies of tantalum nitride thin films prepared by reactive pulsed dc magnetron sputtering

In the present work, the growth characteristics of tantalum nitride (TaN) thin films prepared on (1 0 0) Si substrates by reactive pulsed DC magnetron sputtering are investigated. XRD analyses indicated the presence of alpha-Ta and beta-Ta in the films deposited in pure argon atmosphere, while beta-TaN and fcc-TaN phases appeared for 2 sccm of nitrogen, and cubic TaN for 5-25 sccm of nitrogen in the sputtering gas mixture of argon and nitrogen at a substrate temperature of 773 K. The TaN films obtained with increasing substrate temperature and pulse width showed a change in the texture from [ 1 1 1] to [ 2 0 0] orientation. Atomic force microscopy (AFM) results indicated that the average surface roughness was low for films deposited in pure argon than for the films deposited in a mixed Ar + N(2) atmosphere. Nanocrystalline phase of the deposited material was identified from the high-resolution transmission electron microscopy (HRTEM) images. X-ray photoelectron spectroscopy (XPS) core level spectra confirmed the formation of TaN phase. The high temperature X-ray diffraction analysis of the optimized TaN thin film was performed in the temperature range 298-1473 K. The lattice parameter of the TaN films was found to increase from 4.383 to 4.393 angstrom on increasing the temperature from 298 to 823K and it reduced to 4.345 angstrom at 1473 K. The thermal expansion coefficient value was found to be negative for the TaN films. (C) 2011 Elsevier B.V. All rights reserved.