In situ x-ray diffraction studies concerning the influence of Al concentration on the texture development during sputter deposition of Ti-Al-N thin films

In situ x-ray diffraction was employed during the growth of thin Ti1-ZAlXN films, using a deposition chamber installed at a synchrotron radiation beamline. The films were deposited by reactive cosputtering from Ti and Al targets. In a previous experiment, the substrate temperature, bias voltage, and nitrogen partial pressure, and thus growth rate, were varied at constant x approximate to 0.07. High deposition rates of similar to 1 angstrom/s lead to the typical crossover behavior between initial (001) and final (111) off-plane preferred orientation. Reducing the deposition rate to < 0.5 angstrom/s leads to a reversed behavior with a clear (001) preferred orientation above a film thickness of 600 A, which is essentially independent of the substrate temperature. For the results presented here, the studies were extended to a systemical variation of x from 0 to 0.73 while keeping all the other parameters constant. For a Al concentration up to x similar to 0.15 the (00 1) preferred orientation is persistent. On the other hand, at low deposition rates, a (111) preferred orientation can also be recovered for x > 0.15. This can be addressed to the higher adatom mobility of Al compared to Ti in the presence of atomic nitrogen, which leads to enrichtment of Al in (111) oriented grains. As a consequence, an increase of Al towards the segregation threshold of hexagonal AIN leads to preferred precipitation in (111) oriented grains, reducing the (111) intensity and giving rise to a mixed (111) + (001) texture. Increasing the Al content even further up to x approximate to 0.60 forces the formation of hard nanocomposite ncTiAIN/AIN structures, and finally an Al content of x > 0.73 leads to dominant AIN with an a-axis off-plane texture. (c) 2005 American Vacuum Society.