Metallurgical topics in silicon device interconnections: Thin film stresses

Abstract

Some of the problems encountered in thin film metallisations are presented approximately in chronological order in the introduction with references given to the literature dealing with a variety of topics, such as electromigration. The material which follows has been limited to the issue of stresses in thin films. A consideration of the very general equilibrium of forces between film and substrates is extended to the measurement of stresses in uniform continuous films. In practical conditions with edges and via holes along narrow conductors the stress distributions become greatly more complicated. Intrinsic and extrinsic stresses are discussed with respect both to their origin and to what they mean for technological applications. Stress relaxation is one of the causes for the formation of holes and hillocks. The implications of stresses with respect to adhesion and other practical effects are briefly reviewed.