The interaction between copper and TiN at low temperature.

Sub- and over-stoichiometric TiN films have been processed by varying the flow rate of nitrogen in the chamber. In order to study the copper diffusion through Ti and TiN layers, these layers were systematically coated with a Cu layer 50 nm thick. For some of the stacks a SiN layer 50 nm thick is deposited over the Cu layer. Specimens were isothermally heat treated from 240 to 430 °C under primary vacuum and under argon atmosphere. Cu/BL/SiO/Si and SiN/Cu/BL/SiO/Si stacks (where BL = Ti or TiN) where characterized by transmission electron microscopy with energy dispersive X-ray analysis, time-of-flight secondary ion mass spectrometry and X-ray diffraction. These characterizations indicate clear differences on the copper diffusion through the system depending on the film compositions and microstructures as well as on the annealing temperature. The diffusion of copper through the TiN and the reactivity between Cu and TiN films strongly depend on their composition but also on the processing conditions of these films. Moreover, the performances of some of these films, with respect to copper diffusion and/or reaction, are degraded as the temperature increases from 260 to 430 °C. Diffusion of copper through the TiN films as well as reaction conditions are studied and discussed. [ABSTRACT FROM AUTHOR]