Investigation of TiN films for diffusion barriers in high temperature metallization.

Two groups of reactively sputtered TiN films, gold-yellow films (G films) with low resistivity and high compressive internal stress, and brown-black films (B films) with high resistivity, which are formed with and without the negative substrate bias, were examined for diffusion barrier application.Microstructures and compositions were investigated by AES, EPMA and XD. The G and B films have a fine-grain and a columnar-arranged morphological structure respectively. Both films exhibit a cubic structure strongly oriented toward the (111) plane which is parallel to the substrate surface.The internal stress in the G film originates from lattice expansion which is probably due to the incorporation of the excess nitrogen atoms. The expanded lattice parameter was calculated from the corrected interplanar spacing after the silicon substrate was removed.The superior diffusion barrier capability of the B film, which was demonstrated by the Au/Pt/TiN/Ti metal system on thick polysilicon, was assumed to be due to the reduction of grain boundary diffusion by the action of impurities located in the intercolumnar layers. This is supported by film analysis, etching behavior, and XPS studies.