Abstract
Published results of the multitudinous experiments studying the relationships between the properties and process parameters of sputter deposited TiN films indicate a very complex problem. The complexity manifests itself preferentially in the sporadic formation of the and preferred orientation (PO) and in the sequential formation (crossover) of the and PO in thicker films, even when the deposition parameters are maintained constant during the deposition. The first problem has been clarified by dedicated experiments as well as theoretical works. These revealed that the selection between the development of the and PO is related to the condition of the impinging species, i.e. whether they are neutral or ionized, molecular or atomic Ti and N species, to the degree of ionization, to the ratio of the impinging rates of these species and to their energy as well. Understanding the cross-over formation between the and PO remained, however, an open question so far. As the driving force for this process, the operation of the proposed overall energy minimisation effect, the interplay of the surface and interface and the inner stress energy during thickness growth of the film has been queried.
In the present work authors point out that the complex structural and micro-chemical analysis of the cross-sectional specimens of TiN thin films with PO crossover could provide the fundamental information required to discover the possible phenomena governing the evolution of this particular structure and to reconstruct its pathway. That is demonstrated for the situation when the origin of the to PO crossover could be related to the contamination effect, caused by gas desorption at starting the deposition. In the discussed experiment the TiN film is doped by oxygen and the oxygen concentration changing from 18 to 11 at.% during the deposition.
•Preferred orientation (PO) crossover from to in TiN films is observed.•The PO crossover is due to change of oxygen content built into TiN during growth.•The critical oxygen content below which the PO can develop is about 15 at. %.•The PO crossover occurs by competing of crystals favored by the actual oxygen content.