STRESS AND ANISOTROPY EFFECTS IN THE INTERFACIAL REACTIONS OF AL AND TINX

Structural and compositional analyses of the interfacial region between sputtered TiN(x) (x almost-equal-to 1) and Al films were carried out using X-ray diffraction, transmission electron microscopy, Auger electron spectroscopy and secondary ion mass spectroscopy. It was found that the as-deposited TiN(x) layers, strongly textured along the [111] direction perpendicular to the film surface, were expanded along this direction, with an interplanar spacing larger than that for bulk TiN. This elongation was dependent on the N2/Ar ratio in the gas phase during the film deposition. The TiN(x) film deformation decreased during the subsequent heat treatments. For films with a smaller N2/Ar ratio (excess of Ti), a higher reactivity with Al resulting in Ti aluminides was noted. Another result of this study was an anisotropy of the interfacial processes (interdiffusion and compound formation) as a function of the layer deposition sequences. The Al/TiN(x)/substrate system was found to be much more reactive than was the TiN(x)/Al/substrate system. This may be explained either by the formation of an interfacial Al nitride or oxide prior to the TiN(x) deposition, which blocks the reaction in the case of the TiN(x) deposited on Al, or by point defects (vacancies) which promote the reaction in the case when Al is deposited on TiN(x).