Electrical and Metallurgical Characterization of Niobium as a Diffusion Barrier Between Aluminum and Silicon for Integrated Circuit Devices

Electrical, metallurgical, electromigration, and functional characterizations of an (Al-0.5% Cu)/Nb interconnect metalization for use in 1.2 {mu}m. SRAM integrated circuit devices have been performed. The results indicate that niobium is an excellent diffusion barrier to aluminum and silicon. It is shown that the presence of niobium has significantly improved the electromigration strength (at j = 1.0E7 A/cm/sup 2/) and the thermal and electrical stability of metal to silicon and metal to metal contacts. The barrier characteristics of the niobium were studied electrically (via junction leakage current and contact resistance measurements) and analytically (via TEM examination of aluminum-niobium-silicon interfaces). TEM and electron diffraction analyses show the formulation of the NbAl/sub 3/ phase. It is found that the NbAl/sub 3/ phase has a much slower rate of growth than TiAl/sub 3/ in the temperature range studied.