On the origin of stress in magnetron sputtered TiN layers

Abstract

A recently proposed model has been used to describe the state of stress in magnetron sputtered TiN layers in which the stresses are believed to be caused by atomic peening. The state of stress in the layer is described by a combination of: (i) a hydrostatic state of stress, caused by the introduction of the misfitting atoms, and (ii) a biaxial state of stress induced by the equalization of the lateral dimensions of the substrate and the layer, dilated due to the misfitting atoms and the thermal misfit due to the cooling down of the layer/substrate assembly to room temperature. The implications of the thus obtained total state of stress on x-ray diffraction measurements have been clarified and a quantitative elaboration of the growth stress as a function of the amount and type of misfitting particles has been given. It has been deduced that the growth stresses are caused by about 1 wt % Ti atoms on nitrogen sites in the TiN lattice. By comparing x-ray diffraction results of layers of different thickness, deposited simultaneously on two different substrates, it has been concluded that the growth stress in the layers depends on the layer thickness, whereas the thermal stress is equal for all layers on a given substrate. The observed layer thickness dependence of the growth stress has been associated with a (macro)strain depth profile in the layers. The distinct diffraction line broadening observed for all layers cannot be due to smallness of crystallite size and the macrostrain-depth profiles, it is ascribed to (localized) lattice defects as dislocations and low angle grain boundaries.