The requirements on contact metallurgy for high performance very-large-scale integrated circuit technology have become more and more stringent because of the need for shallow junctions less than 0.25 μm in depth and contact sizes of the order of 1 μm2 or smaller. A deposition of aluminum directly onto single-crystal silicon or onto a metal silicide can no longer satisfy the needs to achieve a stable and reliable contact. The use of a diffusion barrier layer in the contact structure, which prevents metallurgical reactions as well as diffusion between the silicon or silicide and the contact metal, is the most common approach to achieve stable and reliable contacts. The general requirements of such an effective contact barrier will be discussed. Early contact structures as well as diffusion barrier materials currently used in aluminum metallization, such as titanium, W/Ti and TiW, are reviewed and their performance is compared with that of TiN as a contact barrier layer. © 1982.