IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Tuesday Sessions
       Session TF-TuA

Paper TF-TuA8
Thermal Stability of Arc Evaporated Ti@sub 1-x@Al@sub x@N Thin Films

Tuesday, October 30, 2001, 4:20 pm, Room 123

Session: Growth and Properties of Thin Films
Presenter: A. Hörling, Linköping University, Sweden
Authors: A. Hörling, Linköping University, Sweden
L. Hultman, Linköping University, Sweden
M. Odén, Linköping University, Sweden
G. Ramanath, Rensselaer Polytechnic Institute
P.H. Mayrhofer, University of Leoben, Austria
C. Mitterer, University of Leoben, Austria
J. Sjölén, Seco Tools, Sweden
L. Karlsson, Seco Tools, Sweden
Correspondent: Click to Email
The thermal stability of Ti@sub 1-x@Al@sub x@N thin films deposited by arc evaporation from cathodes with nominal composition x=0.67 onto substrates kept at 500°C has been investigated by XRD and TEM, and by differential scanning calorimetry (DSC) and 4-point probe measurements. As-deposited films contained 62 at.% Al and were of cubic [NaCl]-structure phase. Annealing of such metastable films results in relaxation of intrinsic compressive stress, together with spinodal decomposition into cubic TiN and AlN-rich phases succeeded by the precipitation of hexagonal AlN. Stress relaxation was observed to take place for all annealing temperatures above the deposition temperature, which implies that point defects or defect complexes become annihilated. For example, DSC showed enthalpy changes at temperatures up to 700°C, and XRD showed a decrease in peak broadening at temperatures up to 800°C. By XRD, the spinodal decomposition stage was revealed as a symmetrical broadening of the cubic (Ti,Al)N (200) peak after annealing at 900°C; by DSC as an exothermic peak starting at 850°C for a heating rate of 27°C min@super -1@; and by 4-point probe measurements as an increased sheet resistance at 500°C with a maximum at 650°C for a heating rate of 5°C min@super -1@. At higher temperatures, the resistivity decreased, and upon cooling and re-annealing showed a reversible behaviour which indicates a parallel-circuit behaviour of a more TiN-like matrix together with emerging AlN phases. Following spinodal decomposition, phase separation of the structure into c-TiN and h-AlN occurred in the temperature range of 900°C-1100°C, being observed by XRD and TEM. The 4-point probe measurements, especially when compared to XRD, indicate that the heating rate has a large effect on the kinetics of phase separation. This observation will be discussed, together with results of activation energies for the various reactions.