The influence of thermal annealing on residual stresses and mechanical properties of arc-evaporated TiCxN1−x (x=0,  0.15  and  0.45) thin films

✍ Scribed by L. Karlsson; A. Hörling; M.P. Johansson; L. Hultman; G. Ramanath

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 336 KB
• Volume: 50
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(02)00365-8

✦ Synopsis

We report the stress relaxation behavior of arc-evaporated TiC x N 1Ϫx thin films during isothermal annealing between 350 and 900°C. Films with x ϭ 0, 0.15, and 0.45, each having an initial compressive intrinsic stress s int ϭ Ϫ 5.4GPa, were deposited by varying the substrate bias V s and the gas composition. Annealing above the deposition temperature leads to a steep decrease in the magnitude of s int to a saturation stress value, which is a function of the annealing temperature. The corresponding apparent activation energies for stress relaxation are E a ϭ 2.4, 2.9, and 3.1eV, for x ϭ 0, 0.15, and 0.45, respectively. TiC 0.45 N 0.55 films with a lower initial stress s int ϭ Ϫ 3GPa, obtained using a high substrate bias, show a higher activation energy E a ϭ 4.2eV. In all the films, stress relaxation is accompanied by a decrease in defect density indicated by the decreased width of X-ray diffraction peaks and decreased strain contrast in transmission electron micrographs. Correlation of these results with film hardness and microstructure measurements indicates that the stress relaxation is a result of point-defect annihilation taking place both during shortlived metal-ion surface collision cascades during deposition, and during post-deposition annealing by thermally activated processes. The difference in E a for the films of the same composition deposited at different V s suggests the existence of different types of point-defect configurations and recombination mechanisms.