Residual stress and its thermal relaxation in TiN films

The structure and residual stresses of TiN coated films were investigated by X-ray diffraction. TiN films were deposited onto substrates of spring steel by a multi-arc method at different deposition temperatures. The TiN films, approximately 4 mu m in thickness, exhibited high {111} orientation. The residual stresses in the TiN films were evaluated by the two-exposure method to obtain the lattice strains for 222 diffraction at psi = 0 degrees and 70.5 degrees with Cu K alpha radiation. The results revealed very high compressive residual stresses of about -5.8 to -3.5 GPa which are one order larger than the thermal residual stress expected from the thermal strain mismatch between the film and the substrate. These residual stresses in the TiN films decreased on increasing the annealing temperature, and decreased finally to the level of the thermal residual stress after annealing at temperatures above 1073 K.